road map vs plan

road map and plan both are nouns.

Word	Noun	Adjective	Verb	Adverb
road map	Yes	No	No	No
plan	Yes	No	Yes	No

As nouns, plan is a hypernym of road map; that is, plan is a word with a broader meaning than road map:

road map: a detailed plan or explanation to guide you in setting standards or determining a course of action
plan: a series of steps to be carried out or goals to be accomplished

Other hypernyms of road map include program, programme, counsel, counseling, counselling, direction, guidance.

road map (noun)	plan (noun)
a map showing roads (for automobile travel)	scale drawing of a structure
a detailed plan or explanation to guide you in setting standards or determining a course of action	a series of steps to be carried out or goals to be accomplished
	an arrangement scheme

road map (verb)	plan (verb)
	make plans for something
	have the will and intention to carry out some action
	make or work out a plan for; devise