RPKI and offline routes

Can RPKI be used with routes that are not being advertised at the moment? As in to sign a route that *could* be there, but is not there presently. There's been several BGP hijacks that I've followed closely that involved hijacking IP space as well as the ASN that would normally originate it. I'm wondering if having valid ROAs/RPKI would have helped in this case or not. Theodore Baschak - AS395089 - Hextet Systems