Comparing Andre's ability to not need to come to the net with Andy's is comparing apples and oranges. Andre hits everything off the rise, and is almost always in the offensive because of it. He also hits a much flatter ball. Roddick on the other hand stands a few feet behind the baseline, so he has to work much harder to cause UE and hit winners. Roddick also doesn't have the ability to hit winners off of both sides the way Andre does.
Point is, Roddick needs to continue to improve his net game if he is going to want a run at #1. He already proved that when his volleys are solid, he can beat a really tough player(Safin at Indian Wells). In fact, Roddick's results lately have been directly correlated with his success at the net. He's evolving, it will take some time though. His volleys are already heads and tails above last year.