round out vs fill out

round out and fill out both are verbs.

Word	Noun	Adjective	Verb	Adverb
round out	No	No	Yes	No
fill out	No	No	Yes	No

As verbs, round out and fill out are synonyms defined as:

round out (verb)	fill out (verb)
make bigger or better or more complete	become round, plump, or shapely
make round	make bigger or better or more complete
express as a round number	write all the required information onto a form
fill out	make fat or plump
	line or stuff with soft material
	supplement what is thought to be deficient