roll-on roll-off vs railroad train

roll-on roll-off and railroad train both are nouns.

Word	Noun	Adjective	Verb	Adverb
roll-on roll-off	Yes	No	No	No
railroad train	Yes	No	No	No

roll-on roll-off (noun)	railroad train (noun)
a method of transport (as a ferry or train or plane) that vehicles roll onto at the beginning and roll off of at the destination	public transport provided by a line of railway cars coupled together and drawn by a locomotive