pork roast vs roast

pork roast and roast both are nouns.

Word	Noun	Adjective	Verb	Adverb
pork roast	Yes	No	No	No
roast	Yes	Yes	Yes	No

As nouns, roast is a hypernym of pork roast; that is, roast is a word with a broader meaning than pork roast:

pork roast: cut of pork suitable for roasting
roast: a piece of meat roasted or for roasting and of a size for slicing into more than one portion

Other hypernyms of pork roast include joint.

pork roast (noun)	roast (noun)
cut of pork suitable for roasting	negative criticism
	a piece of meat roasted or for roasting and of a size for slicing into more than one portion

pork roast (adjective)	roast (adjective)
	(meat) cooked by dry heat in an oven

pork roast (verb)	roast (verb)
	cook with dry heat, usually in an oven
	subject to laughter or ridicule