Sadly, there aren't enough MSQ and Sidequests available that will allow you to level all 3/(4) of those jobs to 70 without any other supplement. My suggestion would to be:

1. Pick the job you enjoy the most, and level it with the MSQ and experience you get from that. There may be a few instances where you will not receive enough experience to progress to the next MSQ. If that ends up being the case, repeat the highest level dungeon you can until you reach the next level to bypass that level-lock.
2. Take another job, and level it using Sidequest experience. You can also look into using Heavensward beast tribes after you beat the 3.0 MSQ storyline to supplement your experience here-- Heavensward has 2 Beast Tribes, and you can accept 3 quests daily from each, 6 on the days you rank up with them. Experience increases as you rank up higher with each tribe (and the Vanu has a very good story). However, this won't be enough to level the job alone, so you will have to supplement with dungeons, roulettes, and/or PotD.
3. Any other jobs you want to cap out at 70, you will have to use dungeons and/or PotD to level them.

This game sadly does not provide enough Sidequests/experience per Sidequest to allow players to level jobs solely off of the Sidequests, so you will always end up having to supplement with experience from other sources. Leveling roulette is excellent for leveling other jobs, so I would definitely recommend running it every day for the roulette bonus.

Hope this helps!