What do u mean when you say a round cafe? Do u mean a round top such as a dome, Victorian, roman, or do u mean a circular shaped cage?
A round top is fine, u can choose any styling that suits u, however a flat top or a play gym top gives an area for the grey to forage.
A round cage is a big big no no! The cage should have distinct 4 corners! And try to put the cage in a place where at least one side is against the wall. All of this is important to make your grey feel more secure and less wary ofcourse.
Cheers