devious vs roundabout

devious is not a noun while roundabout is a noun.

Word	Noun	Adjective	Verb	Adverb
devious	No	Yes	No	No
roundabout	Yes	Yes	No	No

As adjectives, devious and roundabout are synonyms defined as:

Other synonyms of devious include circuitous.

devious (noun)	roundabout (noun)
	a road junction at which traffic streams circularly around a central island
	a large, rotating machine with seats for children to ride on for amusement

devious (adjective)	roundabout (adjective)
deviating from a straight course	deviating from a straight course
indirect in departing from the accepted or proper way; misleading	marked by obliqueness or indirection in speech or conduct
characterized by insincerity or deceit; evasive