roundup vs round up

roundup is a noun but round up is not a noun.

Word	Noun	Adjective	Verb	Adverb
roundup	Yes	No	No	No
round up	No	No	Yes	No

roundup (noun)	round up (noun)
the systematic gathering up of suspects by the police
the activity of gathering livestock together so that they can be counted or branded or sold
a summary list; as in e.g. "a news roundup"

roundup (verb)	round up (verb)
	seek out and bring together