rock music vs rock 'n' roll

rock music and rock 'n' roll both are nouns.

Word	Noun	Adjective	Verb	Adverb
rock music	Yes	No	No	No
rock 'n' roll	Yes	No	No	No

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

rock music and rock 'n' 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, rock and roll.

rock music (noun)	rock 'n' 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