If at least one ROA matches a route, then the route is valid.
This is to cover the case when more than one AS is authorized to
originate a particular prefix.
o NotFound: No VRP Covers the Route Prefix.
o Valid: At least one VRP Matches the Route Prefix.
o Invalid: At least one VRP Covers the Route Prefix, but no VRP
BTW, this rule allows you to issue a ROA authorizing AS0 to originate
your complete address space.
Why would you do that? Suppose you own an address space, but you only
want to announce a portion of it to the internet. If you issue a ROA
for the unannounced portion authorizing your own ASN, then an attacker
can announce that portion and prepend your ASN. The attacker can thus
hijack your unannounced space and appear valid by RPKI!
To prevent that, you issue a ROA for your complete address space
authorizing AS0 and your BGP announced space authorizing your own ASN.
An AS path containing AS0 is malformed, being treated as withdraw.