A lot of it is situational, but I've found I can keep a party happy with:
Corsair's Roll - you're going to have it anyway, I rarely use it, but some people request it and I've used it when there's been a BRD about - they can focus on other buffs leaving space for a Corsair's roll.
Ninja's Roll - Situational, normally flag it when we're struggling with mobs and I figure if it means people get fewer hits, then the extra eva is useful.
Hunter's Roll - ACC+ is always useful, particularly when it comes to using ranged attacks. A bonus for lower level parties because people aren't really geared for accuracy - people still occassionally miss in high level parties, so the fewer misses there are, the more damage is being dealt
Chaos Roll - ATT+ is also useful, people like being able to hit harder
Healer's Roll - Handy Pre-level 40, it'll keep your mages happy in that they don't have to rest as long to restore MP. If your mages are down, even after level 40, it's useful to have.
Evoker's Roll - An asset for your mages and they will love you for it, even if you have a Red Mage in the party because it will stack on top of Refresh AND Sublimation (sublimation will replace refresh) and it will stack on top of BRD songs as well. Refresh is a good thing.


You can survive for a while on those. There's other ones that are useful, but I figure these are pretty cost effective.