rock-and-roll vs popular music

rock-and-roll and popular music both are nouns.

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

As nouns, popular music is a hypernym of rock-and-roll; that is, popular music is a word with a broader meaning than rock-and-roll:

rock-and-roll: a genre of popular music originating in the 1950s; a blend of black rhythm-and-blues with white country-and-western
popular music: any genre of music having wide appeal (but usually only for a short time)

Other hypernyms of rock-and-roll include popular music genre.

rock-and-roll (noun)	popular music (noun)
a genre of popular music originating in the 1950s; a blend of black rhythm-and-blues with white country-and-western	any genre of music having wide appeal (but usually only for a short time)