AaronOfBarbaria
Adventurer
Whatever you want, because that is the answer no matter who is asking what to play - "party composition" be damned. Play what sounds like fun, and it usually is.
I voted rogue since the bard could pinch-hit for a mage, but I guess he could act as a rogue as well. You seem to have combat down fairly well with the barbarian and paladin. Healing looks good with cleric and paladin. I could go either mage or rogue, but I tend to like rogues more.