roller vs garden roller

roller and garden roller both are nouns.

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

As nouns, garden roller is a hyponym of roller; that is, garden roller is a word with a more specific, narrower meaning than roller:

Other hyponyms of roller include paint roller, platen, sprocket, trundle.

roller (noun)	garden roller (noun)
a grounder that rolls along the infield	heavy cast-iron cylinder used to flatten lawns
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