In al my MMO guilds finding healers or tanks was not a problem at all.
Finding people that were actually good at their class was, esp. dps ones!
So i'd say just roll a class with a playstyle that you like: melee dps, melee tank, ranged tank, healing or ranged dps..
And ofcourse have some friends rolling tanks/healers and dps so you can always get a group for flashpoints