Roman Church vs Roman Catholic Church

Roman Church and Roman Catholic Church both are nouns.

Word	Noun	Adjective	Verb	Adverb
Roman Church	Yes	No	No	No
Roman Catholic Church	Yes	No	No	No

As nouns, Roman Church and Roman Catholic Church are synonyms defined as:

Roman Church and Roman Catholic Church: the Christian Church based in the Vatican and presided over by a pope and an episcopal hierarchy

Other synonyms of Roman Church include Church of Rome, Roman Catholic, Western Church.

Roman Church (noun)	Roman Catholic Church (noun)
the Christian Church based in the Vatican and presided over by a pope and an episcopal hierarchy	the Christian Church based in the Vatican and presided over by a pope and an episcopal hierarchy