You guys realize that the difference is size between a 90 sq. inch head and a 95 is truly small, right? As anyone who has hit the K90/BLX90 as opposed to the K95 or BLX95 will tell you, these are very different racquets. So, it is not like Roger could just use a normal Wilson 95. I understand they are pros playing with a box Wilson 95, but who knows how close it would be to the feel of Roger's current stick.
Look, Roger may shank a few more balls than other top ten players, but I don't think his racquet choice plays a big part in that. I think he shanks because, one, he plays closer to the baseline to take time away from his opponent more than many other players do which obviously reduces his preparation time and two, he brushes up very quickly on the ball to impart top spin. This means there is less surface string area to strike the ball and more chance for the frame to make contact with the ball. Agassi also took the ball early (he was the best ever at it), but his strokes were flatter which reduced the possibility of his framing the shot.
As others have said, I think Roger is the best judge of what racquet works for him.