rock music vs rock and roll

rock music and rock and roll both are nouns.

Word	Noun	Adjective	Verb	Adverb
rock music	Yes	No	No	No
rock and roll	Yes	No	No	No

As nouns, rock music and rock and roll are synonyms defined as:

rock music and rock and roll: a genre of popular music originating in the 1950s; a blend of black rhythm-and-blues with white country-and-western

Other synonyms of rock music include rock-and-roll, rock'n'roll, rock 'n' roll, rock.

rock music (noun)	rock and roll (noun)
a genre of popular music originating in the 1950s; a blend of black rhythm-and-blues with white country-and-western	a genre of popular music originating in the 1950s; a blend of black rhythm-and-blues with white country-and-western