hip roof vs hipped roof

hip roof and hipped roof both are nouns.

Word	Noun	Adjective	Verb	Adverb
hip roof	Yes	No	No	No
hipped roof	Yes	No	No	No

As nouns, hip roof and hipped roof are synonyms defined as:

hip roof and hipped roof: a roof having sloping ends as well as sloping sides

hip roof (noun)	hipped roof (noun)
a roof having sloping ends as well as sloping sides	a roof having sloping ends as well as sloping sides