papist vs Romanist

papist is a noun but Romanist is not a noun.

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

As adjectives, papist and Romanist are synonyms defined as:

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

papist (noun)	Romanist (noun)
an offensive term for Roman Catholics; originally, a Roman Catholic who was a strong advocate of the papacy

papist (adjective)	Romanist (adjective)
of or relating to or supporting Romanism	of or relating to or supporting Romanism