roller skate vs roller

roller skate and roller both are nouns.

Word	Noun	Adjective	Verb	Adverb
roller skate	Yes	No	Yes	No
roller	Yes	No	No	No

roller skate (noun)	roller (noun)
a shoe with pairs of rollers fixed to the sole	a grounder that rolls along the infield
	Old World bird that tumbles or rolls in flight; related to kingfishers
	pigeon that executes backward somersaults in flight or on the ground
	a cylinder that revolves
	a mechanical device consisting of a cylindrical tube around which the hair is wound to curl it
	a small wheel without spokes (as on a roller skate)
	a long heavy sea wave as it advances towards the shore

roller skate (verb)	roller (verb)
travel on shoes with steel or rubber rollers attached to their soles