laugh at vs roast

laugh at is not a noun while roast is a noun.

Word	Noun	Adjective	Verb	Adverb
laugh at	No	No	Yes	No
roast	Yes	Yes	Yes	No

As verbs, laugh at and roast are synonyms defined as:

Other synonyms of laugh at include blackguard, guy, jest at, make fun, poke fun, rib, ridicule.

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

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

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