Roundhead vs champion

Roundhead and champion both are nouns.

Word	Noun	Adjective	Verb	Adverb
Roundhead	Yes	No	No	No
champion	Yes	Yes	Yes	No

As nouns, champion is a hypernym of Roundhead; that is, champion is a word with a broader meaning than Roundhead:

Roundhead: a supporter of parliament and Oliver Cromwell during the English Civil War
champion: a person who backs a politician or a team etc.

Other hypernyms of Roundhead include admirer, booster, friend, protagonist, supporter.

Roundhead (noun)	champion (noun)
a supporter of parliament and Oliver Cromwell during the English Civil War	someone who fights for a cause
	someone who has won first place in a competition
	a person who backs a politician or a team etc.
	someone who is dazzlingly skilled in any field

Roundhead (adjective)	champion (adjective)
	holding first place in a contest

Roundhead (verb)	champion (verb)
	protect or fight for as a champion