wassail vs roister

wassail is a noun but roister is not a noun.

Word	Noun	Adjective	Verb	Adverb
wassail	Yes	No	Yes	No
roister	No	No	Yes	No

As verbs, roister is a hyponym of wassail; that is, roister is a word with a more specific, narrower meaning than wassail:

wassail: celebrate noisily, often indulging in drinking; engage in uproarious festivities
roister: engage in boisterous, drunken merrymaking

Other hyponyms of wassail include carouse, riot.

wassail (noun)	roister (noun)
a punch made of sweetened ale or wine heated with spices and roasted apples; especially at Christmas

wassail (verb)	roister (verb)
propose a toast to	engage in boisterous, drunken merrymaking
celebrate noisily, often indulging in drinking; engage in uproarious festivities