roselle vs hibiscus

roselle and hibiscus both are nouns.

Word	Noun	Adjective	Verb	Adverb
roselle	Yes	No	No	No
hibiscus	Yes	No	No	No

As nouns, hibiscus is a hypernym of roselle; that is, hibiscus is a word with a broader meaning than roselle:

roselle: East Indian sparsely prickly annual herb or perennial subshrub widely cultivated for its fleshy calyxes used in tarts and jelly and for its bast fiber
hibiscus: any plant of the genus Hibiscus

roselle (noun)	hibiscus (noun)
East Indian sparsely prickly annual herb or perennial subshrub widely cultivated for its fleshy calyxes used in tarts and jelly and for its bast fiber	any plant of the genus Hibiscus