Tough luck, but its his face, so it won't affect his game and it should be a short timetable for return. Same thing Westbrook and Rondo had last year.
Not quite; there's several different bones that comprise the face.
Westbrook broke the lateral process of his zygomatic bone (his cheek). From all of the reports about D-Rose's injury, it's much closer to his eye and, as a result, is a more serious injury (as there could be potential complications with his vision). That wasn't really a concern with Westbrook as the injury was far from his eyes; that's why he was able to return after missing a single game.
Rose should be good for the season opener, but he won't be able to (or probably more accurately, shouldn't) make a Westbrook-style return, i.e. return during training camp or even during preseason.