a roof job is when a chick lays on her back on a bed or coach or other similar surface (preferrably butt ass naked) with her head hanging over the edge. the dude then straddles her head, grabs her by her hair and/or ears, shoves his cock into her mouth and begins to bang for all he's worth - effectively knocking the shingles off the roof of her mouth
when a considerably tall man gets a considerably short girl to get on her knees and suck his cock. the necessity of the short girl to stretch her head and neck in the upward position to reach the cock achieves the same effect of the roof of her mouth getting the shit banged out of it. Let's not forget the hair, head, neck grabbing to get the appropriate amount of banging and gagging. :)
HOLLY SHIT JM, that was the best roof job i ever had. it knocked those pesky wisdom teeth out saving me a dentist appointment and i cant feel my chin anymore!!!! You think FEMA will cover THIS roof damage?!?!?!?