hot cross bun vs sweet roll

hot cross bun and sweet roll both are nouns.

Word	Noun	Adjective	Verb	Adverb
hot cross bun	Yes	No	No	No
sweet roll	Yes	No	No	No

As nouns, sweet roll is a hypernym of hot cross bun; that is, sweet roll is a word with a broader meaning than hot cross bun:

hot cross bun: moderately sweet raised roll containing spices and raisins and citron and decorated with a cross-shaped sugar glaze
sweet roll: any of numerous yeast-raised sweet rolls with our without raisins or nuts or spices or a glaze

Other hypernyms of hot cross bun include coffee roll.

hot cross bun (noun)	sweet roll (noun)
moderately sweet raised roll containing spices and raisins and citron and decorated with a cross-shaped sugar glaze	any of numerous yeast-raised sweet rolls with our without raisins or nuts or spices or a glaze