character actor vs role player

character actor and role player both are nouns.

Word	Noun	Adjective	Verb	Adverb
character actor	Yes	No	No	No
role player	Yes	No	No	No

As nouns, role player is a hypernym of character actor; that is, role player is a word with a broader meaning than character actor:

Other hypernyms of character actor include actor, histrion, player, thespian.

character actor (noun)	role player (noun)
an actor who specializes in playing supporting roles	a theatrical performer
	a person who makes deceitful pretenses