roof vs curb roof

roof and curb roof both are nouns.

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

As nouns, curb roof is a hyponym of roof; that is, curb roof is a word with a more specific, narrower meaning than roof:

roof (noun)	curb roof (noun)
a protective covering that covers or forms the top of a building	a roof with two or more slopes on each side of the ridge
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

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