obstacle vs roadblock

obstacle and roadblock both are nouns.

Word	Noun	Adjective	Verb	Adverb
obstacle	Yes	No	No	No
roadblock	Yes	No	No	No

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

obstacle: something immaterial that stands in the way and must be circumvented or surmounted
roadblock: any condition that makes it difficult to make progress or to achieve an objective

Other hyponyms of obstacle include barrier, hang-up, hitch, rub, snag, hurdle, stymie, stymy.

obstacle (noun)	roadblock (noun)
an obstruction that stands in the way (and must be removed or surmounted or circumvented)	a barrier set up by police to stop traffic on a street or road in order to catch a fugitive or inspect traffic etc.
something immaterial that stands in the way and must be circumvented or surmounted	any condition that makes it difficult to make progress or to achieve an objective