You also receive a small % of stats added onto arena...at least that is what mods said.

Roshi is not a tank, but many here (not iamascrub) continue to think he is just because he stacks defense. Roshi in arena needs to be exposed to damage but not to the highest part of it. Works well with han or hokage minato or with bee sst that shields him or behind clones. Hardly even kimimaro, that's a real tank, survives if fully exposed to damage with no shields or defense buffs.