walk-on vs role player

walk-on and role player both are nouns.

Word	Noun	Adjective	Verb	Adverb
walk-on	Yes	Yes	No	No
role player	Yes	No	No	No

As nouns, role player is a hypernym of walk-on; that is, role player is a word with a broader meaning than walk-on:

Other hypernyms of walk-on include actor, histrion, player, thespian.

walk-on (noun)	role player (noun)
plays a small part in a dramatic production	a theatrical performer
	a person who makes deceitful pretenses

walk-on (adjective)	role player (adjective)
not capable of or especially not involving speech or spoken lines