role vs second fiddle

role and second fiddle both are nouns.

Word	Noun	Adjective	Verb	Adverb
role	Yes	No	No	No
second fiddle	Yes	No	No	No

As nouns, second fiddle is a hyponym of role; that is, second fiddle is a word with a more specific, narrower meaning than role:

role: the actions and activities assigned to or required or expected of a person or group
second fiddle: a secondary role or function

Other hyponyms of role include capacity, hat, portfolio, lieu, place, position, stead.

role (noun)	second fiddle (noun)
the actions and activities assigned to or required or expected of a person or group	a secondary role or function
normal or customary activity of a person in a particular social setting	someone who serves in a subordinate capacity or plays a secondary role
what something is used for
an actor's portrayal of someone in a play