roof vs slate roof

roof and slate roof both are nouns.

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

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

roof (noun)	slate roof (noun)
a protective covering that covers or forms the top of a building	a roof covered with slate
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)	slate roof (verb)
provide a building with a roof; cover a building with a roof