rooftop vs roost

rooftop

• The area atop a roof. 

• The top layer of a roof; the material covering or composing a roof. 

roost

• The inner roof of a cottage. 

• A group of birds roosting together. 

• A tidal race. 

• A bedroom 

• The place where a bird sleeps (usually its nest or a branch). 

• to spend the night 

• To settle on a perch in order to sleep or rest