roasting vs barbecuing

roasting and barbecuing both are nouns.

Word	Noun	Adjective	Verb	Adverb
roasting	Yes	No	No	No
barbecuing	Yes	No	No	No

As nouns, barbecuing is a hyponym of roasting; that is, barbecuing is a word with a more specific, narrower meaning than roasting:

roasting: cooking (meat) by dry heat in an oven (usually with fat added)
barbecuing: roasting a large piece of meat on a revolving spit out of doors over an open fire

roasting (noun)	barbecuing (noun)
cooking (meat) by dry heat in an oven (usually with fat added)	roasting a large piece of meat on a revolving spit out of doors over an open fire