roll over vs rollover

roll over is not a noun while rollover is a noun.

Word	Noun	Adjective	Verb	Adverb
roll over	No	No	Yes	No
rollover	Yes	No	No	No

roll over (noun)	rollover (noun)
	the act of changing the institution that invests your pension plan without incurring a tax penalty

roll over (verb)	rollover (verb)
make a rolling motion or turn
re-invest (a previous investment) into a similar fund or security
negociate to repay a loan at a later date for an additional fee