i always got confused with what grip he uses
i think this sums it up pretty much.
Modern Classic - Roger Federer's Forehand
Roger Federer’s forehand is the most beautiful, versatile, and powerful weapon in pro tennis. It may also be the most misunderstood. We’ll dissect four major elements of this superb stroke.
By John Yandell
Many people think Roger Federer plays with a semi-Western grip, similar to Andy Roddick’s. In reality, his grip is closer to Pete Sampras’. Federer keeps part of his hand off the end of the grip, but most of it is still on the back of the handle, directly aligned with the face of the racquet. He shifts his index base knuckle slightly downward about half a bevel toward a semi-Western grip (to do this, stand the racquet on its end, as in the diagram below, and place your index base knuckle between bevels 3 and 4 if you’re right-handed or between 6 and 7 if you’re a lefty). This modiﬁ ed Eastern grip is more conservative than that of most top players, who typically shift farther toward the Western grip and place part or most of their hands under the handle. This grip allows for the ideal contact height for a player who stands close to the baseline and plays the ball early, a key to Federer’s effectiveness.