upside vs rooftop

upside and rooftop both are nouns.

Word	Noun	Adjective	Verb	Adverb
upside	Yes	No	No	No
rooftop	Yes	No	No	No

As nouns, rooftop is a hyponym of upside; that is, rooftop is a word with a more specific, narrower meaning than upside:

Other hyponyms of upside include crest, crown, poll, crown, pate, poll, desktop, tiptop.

upside (noun)	rooftop (noun)
the highest or uppermost side of anything	the top of a (usually flat) roof