That's the only big doubt - Roddick's power game. But if he's even slightly off, Fed will punish him and do it well.
Personally I think it's most likely to happen if Roddick wins the first set - it might settle him down a little too much and fire Fed up farrr too much.
Really, I think it will be a really tough four or five set game - but considering how dominant Federer is at grand slams, it screams "OVERS!!". Not likely to happen, but having $3 or so on each isn't the worst investment in the world.