Why both a route object and a ROA
A route object in an IRR (RIPE DB, RADB) says “this prefix belongs to that AS”; providers and IXPs build filters from it. A ROA in RPKI is a cryptographically signed statement of the same thing; routers with ROV drop announcements with a wrong origin. Today you need both: without a route object an upstream may not accept the announcement, without a ROA your prefix is “unknown” and not protected from hijacks.
Which maxLength to use
Safest is maxLength equal to the prefix length plus a separate ROA for each more-specific you really announce (RFC 9319). A broad maxLength “just in case” lets an attacker announce a subnet with your AS in the path and hijack traffic, and RPKI will not stop it.
How to check after changes
15–60 minutes after creating ROAs, each prefix status shows up in the BGP and RPKI check; all prefixes of a network are in autonomous systems and can be merged in the CIDR aggregator.