popish vs Roman

popish is not a noun while Roman is a noun.

Word	Noun	Adjective	Verb	Adverb
popish	No	Yes	No	No
Roman	Yes	Yes	No	No

As adjectives, popish and Roman are synonyms defined as:

Other synonyms of popish include papist, papistic, papistical, R.C., Roman Catholic, Romanist, romish.

popish (noun)	Roman (noun)
	a resident of modern Rome
	an inhabitant of the ancient Roman Empire

popish (adjective)	Roman (adjective)
of or relating to or supporting Romanism	of or relating to or supporting Romanism
	of or relating to or derived from Rome (especially ancient Rome)
	characteristic of the modern type that most directly represents the type used in ancient Roman inscriptions