roarer vs bellower

roarer and bellower both are nouns.

Word	Noun	Adjective	Verb	Adverb
roarer	Yes	No	No	No
bellower	Yes	No	No	No

As nouns, roarer and bellower are synonyms defined as:

roarer and bellower: someone who communicates vocally in a very loud voice

Other synonyms of roarer include bawler, screamer, screecher, shouter, yeller.

roarer (noun)	bellower (noun)
someone who communicates vocally in a very loud voice	someone who communicates vocally in a very loud voice