Okay, I'm quite interested in getting involved in the RPG, but there are a few different lists of which characters are available. It's pretty mind-boggling and can't figure which is which. So, which characters are available..? (I probably sound stupid, but I don't care. )
Oz did not rejoin the team after that adventure. Also, since we are skipping ahead for a year, his whereabouts and activities for that time period are completely open. If you were to be cast as that (or any) character, you would have some leeway in determining what your character had been up to during that time period. That said, as with any RPG, the majority of the action would be focused on the present. In this case, that would mean that prior events would have driven Oz to choose and join one side of the slayer war.