sprocket vs roller

sprocket and roller both are nouns.

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

As nouns, roller is a hypernym of sprocket; that is, roller is a word with a broader meaning than sprocket:

sprocket (noun)	roller (noun)
thin wheel with teeth that engage with a chain	a grounder that rolls along the infield
tooth on the rim of gear wheel	Old World bird that tumbles or rolls in flight; related to kingfishers
roller that has teeth on the rims to pull film or paper through	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