Roman vs European

Roman and European both are nouns.

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

As nouns, European is a hypernym of Roman; that is, European is a word with a broader meaning than Roman:

Roman (noun)	European (noun)
a resident of modern Rome	a native or inhabitant of Europe
an inhabitant of the ancient Roman Empire

Roman (adjective)	European (adjective)
of or relating to or supporting Romanism	of or relating to or characteristic of Europe or the people of Europe
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