How do the rosters work when MLB teams complete a suspended game?

I read that tomorrow, the Yankees and Orioles are resuming a previously suspended game, in the 8th inning with runners on base and A-Rod on deck, etc. How does the roster work in those games? Presumably, both teams have traded, optioned, and waived players who were on their roster at that time. What if the guy on 2nd base got traded? Or if the Orioles pitcher now plays for the Yankees? It didn't happen here, but suppose it did. Can a player wind up playing for both teams in the same game? Who gets to play and who doesn't?