Is Roddick playing doubles with Melzer? I think that's a smart, low-expectation move for him, just to get used to the movement and to work on the volley on clay, which you have to be able to do to close out points there.
Also, I think Andy will volley competently in doubles -- his problem in singles is more transition, grip change, and anticipation/positioning than it is technique -- but his weak service return will hurt him.
The big question is -- will Melzer break out that crazy two-handed drop shot in doubles play?