Returning Player Trying to Remember Dungeons

I've been playing off and since release, but have been gone for a long time. I returned a month ago and it took me about a week just to relearn basic stuff, like the interface, plus the changes since I last played.

First of all, is there a way of knowing in advance when I choose a daily roulette, which ones I previously unlocked? After years away, playing other games, there's not a chance I can remember them.

What I did instead was play a low level job, then found a list of dungeons and watched videos for dungeons that were lower level than the job. That worked well, until that job reached 49. Titan was not on that list, but I did happen to remember it (yeah, I know it's not considered a dungeon).

At level 50, there are at least 19 dungeons, many of which I unlocked, but can't remember which.

What I would like to do is be able to know which ones I've unlocked so that I can review them, as would a newb. But I just want to do this to get back to where I was when I last played.

I do remember the days when videos didn't exist and we had to figure it for ourselves. Those days are long gone, and any new with any sense would watch a video to learn what to expect.

Or are all of you OK with new/returning players not having a clue in roulettes, so I should quit worrying about it?

dungeons are hardly worth being worried/fussed over. save that for any extreme trials. just wing it and you'll be fine.

Generally speaking: Dungeons are so easy that it usually doesnt matter wether you know or remember them - and people usually dont mind newbies/returners messing some things up, as long as they're showing that they're trying to learn from their mistakes.

I dont think its worth to try and remember every dungeon in the game - however, there are mechanics that are repeated over and over again (sometimes with a slightly different animation or color) and its worth knowing those by heart. That way you dont need to know whats mechanics a boss will do excatly, but can adapt quickly to whatever appears on screen.

Heres a list of mechanics that I think would be worth to remember:
Avoid AoEs: Hopefully very obvious, but: Dont stand in big circles that appear on the ground. Usually orange. Sometimes bosses will place AoE/debuff/DoT-zones on the field, like (green) poison puddles or (red) zones in which you'll get a bleed. Dont stand in those. If you notice that you have a dot or debuff and the ground beneath your feet looks funny, move a bit to the side.
Dont stand infront of the boss: Unless you're a tank you have no place standing infront of the boss. If the boss turns around, its usually a good idea to move a bit to the side - it could be a sign that the boss is going to shoot something in the direction hes now facing. Around the boss is a circle with a little arrow that shows where the face/front of the boss is - if you have difficulty telling by the model, you can take a look at this circle instead.
Killing Adds: Yes, there are a couple of fights where adds can be ignored. And there are quite a few where ignoring the adds means a wipe or waste of time. Unless someone specifically mentions to ignore the adds, try to kill anything thats not the boss before dpsing the boss (again).
Stack marker: Usually an orange/yellow-ish circle AoE around a person with a big arrow pointing towards the middle. That means that this person will take a huge amount of damage that needs to be shared amongst multiple people. If you get such a marker, run towards your party and/or into the middle and/or towards the tank and then stand still. If someone else gets such a marker, run to them. Using shields before the hit and healing everyone up afterwards is a good idea aswell.
Spread marker: These come in a couple different flavours, the most common one is probably an orange crystal that appears above your head. In broader terms, I'd say that its not a bad idea to learn what the stackmarker looks like and assume that everything else is a spread marker - aka: if you get one like that, get away from everyone else. If the spread marker includes an AoE around you, try not to hit other people with that aswell. Since some spread markers will result in cone- or line-AoEs being shooted towards you, its a good idea to try to spread around the outside of the arena and keep the middle safe.
Chains: Chains will usually bind two players together - indicated by a debuff-icon aswell as an orange chain that appears between the two players. In most cases you need to break the chain by running away from the player you're bound to - there are little expections where you need to stand close together, though. Not breaking the chain usually results in some debuffs and/or damage taken. Run away from your chain-partner (sometimes it requires quite a distance) and if that doesnt help, try running towards them.
Theters/Chains between enemies: Sometimes enemies will theter to each other. Most of the time adds will theter to the boss and most of the time it will make the boss invulnerable (boss will get an icon and wont take damage. Esay to tell by the huge 0 the game will show you if you attack it). Kill the adds, then proceed with the boss.
Look away!: If you see a big, purple eye appear above a mobs head, its time to turn your back to that enemy or else you'll take damage/get a debuff/be turned into stone etc.
Towers: Circle AoE-markers on the ground with a pillar/tower in the middle, usually there are multiples of those. Each one needs a person in it or it will explode for raidwide damage and/or debuff.
Meteors: Very similar to tower - again circle AoEs on the ground, usually with an orb floating in the middle. They light up if a person steps into them. The person inside the meteor will take a bit of damage, but it prevents the meteor from exploding for raidwide damage and/or debuffs, so its worth it. If you see a meteor: go and stand in it. One person is enough, though.
Spinning bosses: This became popular in Stormblood - the boss will start to turn either clockwise or anti-clockwise will performing some sort of cone-attack (often a breath from the front). Arrows on the side of the boss show in which direction it will turn and you need to run around the boss, following that movement, to stay in a safe place. If you see huge arrows appear on the side of the boss, get close to its hitbox and prepare to run around.
Esuna: The game will now show you which dots and debuffs can be removed by using Esuna - if the dot/debuff has a white line under the icon, you can and should remove it using Esuna.
Interrupt/Silence: Likewise, the game will now show you wether or not a cast can be interrupted: If there is a white, pulsing outline around the castbar, you can use your Interrupt-skill (if you're a tank, melee or ranged dps) to avoid that cast from being completed. Not a 100% needed but always nice to prevent huge damage going out or debuffs being applied to the whole group.
Special actions: By this I mean both the duty-actions aswell as enviroment that cane be used. Duty-actions only apply in a handful of fights and are highly situational, so I'm just mentioning them to make you aware of these. Using the enviroment happens a bit more often, I'd say - usually in the form of some kind of "teleporter" that gets placed on the field, most likely a blue circle (maybe with some flavour added, like a water-sprout or something). If your teammates suddenly disappear, they probably used such a teleporter - look for something with a blue circle and/or name displayed and see if it gets you to a new place!

This might not cover everything and there are a few specific AoE-patterns that are worth remembering because they're being reused.
The important bits for dungeons are pretty much limited to: Dodge AoEs, kill adds, dont be in front of the boss, stack with your party if needed, get away from your party otherwise (but not so far that AoE-heals cant hit you anymore).
Trashpulls are pretty much limited to: Avoid ground-AoEs if you can, heal the tank as much as needed, kill the trash. Theres no mechanics to them that absolulty need to be performed.

Having no clue at all on how to handle basic mechanics like a stackmarker is pretty annoying - if you have that basic knowledge however and are able to apply it "on the fly" in a dungeon you dont know/remember, showing up without a clue about the dungeon itself is not a problem, though. A quick "Hey, I'm new" or "This one has been a while" at the start while showing that you're willing to take (friendly) advice and are trying your best to apply that advice/improve can help aswell.
No one expects anyone to know every dungeon like the back of their hand.

The level 50 duties sometimes have mechanics you cannot derp your way through, usually the (Hard) dungeons.
If you're concerned, just avoid those and you should be fine.

You could just... look through the list of duties you have available on all the tabs that aren't the roulette tab?

Thank you to all who replied! Each and everyone of you have helped me a lot to get over my fear of using the duty finder, in very different ways, but all equally important and helpful to me.

And you have reminded me about the best feature of FF14 - it has the nicest players of any multiplayer game I've ever played.

Yeah, i was gonna say what Hasrat said. Open your dungeon list in the duty finder and it will show you the dungeons(and raids and trials) you have unlocked. The "Leveling" roulette has the Ifrit, Titan, and Garuda 4 man fights along with all the non-cap dungeons. The "Trials" is just all the 8 man(non-extreme) trials you have unlocked. The MSQ roulette is Castrum and Prae. The x0 dungeon roulette is the cap dungeons from all the older expansions(so lvl 50 ARR dungeons, lvl 60 HW dungeons, etc). The "Alliance" roulette is all the 24 man raids youve unlocked(CT series for ARR, Shadows of Mhach for HW, etc). Frontline is a roulette that rotates through the PvP modes daily. Guildhests have their own roulette. And you probly arent far enough along to have unlocked the Normal, 80, Mentor, or Expert roulettes.

You can pretty much wing all the dungeons with the general information Vidu provided.
The only outliers in terms of mechanics are the level 50 ARR dungeons because some mechanics aren't really intuitive and can't be summed up by "don't stand in bad" etc., so if you want to take your time to get a hang of everything and not worry about screwing up, not doing 50/60/70 roulette could help you. Besides, it's not really a good roulette in terms of reward anyway.
60/ 70 dungeons are once again pretty straightforward and can easily be winged by just watching what's going on and taking a somewhat educated guess.