Romanist vs Roman

Romanist is not a noun while Roman is a noun.

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

As adjectives, Romanist and Roman are synonyms defined as:

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

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

Romanist (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