Coming from Icecrown

Hi guys, as the title says I am coming from Icecrown and am just wondering what's the most needed roles here between tanks and healers.
I play both mostly DK for tanking but also Warrior and healing I am normally a Shammy but I've also played Priest. So yeah, just curious as to what I should roll as, thanks for any replies :D

pretty much anything goes, except if you want to raid high end, warrior tanks arent that great and resto druids also tend to underpreform on many fights. but other than that, whatever you choose to play, you will most likely get a spot in a raid.