gable roof vs roof

gable roof and roof both are nouns.

Word	Noun	Adjective	Verb	Adverb
gable roof	Yes	No	No	No
roof	Yes	No	Yes	No

As nouns, roof is a hypernym of gable roof; that is, roof is a word with a broader meaning than gable roof:

gable roof (noun)	roof (noun)
a double sloping roof with a ridge and gables at each end	a protective covering that covers or forms the top of a building
	protective covering on top of a motor vehicle
	an upper limit on what is allowed
	the inner top surface of a covered area or hollow space

gable roof (verb)	roof (verb)
	provide a building with a roof; cover a building with a roof