I tried to research which Skyhawks had sunroofs and failed to find out anything. It may have just been an option after some point in the late 70s up to stoppage of production in 1986. You sure don't see many pf them, and I could not even find a picture of one to post. It was a set of dual, fixed, smoke color plexiglass panels above the pilot and copilot. It probably did not get sold very often or they would do it now. The current Skyhawks have a large console above the front seats which would be hard to do away with. But it was a neat option.
A lot of the skydiver modified Cessnas have a swing up door with a lower window in it. Very nice feature, it really enhances the flight experience and allows for better ground observation.