These entries are queried from radb.net using whois, you can try my project getting these.
:AS53537 route: 199.21.248.0/22 descr: ISG Software Group, LLC origin: AS53537 mnt-by: ONECOMM-MNT changed: erioux [at] onecommunications.com 20101018 source: LEVEL3 rpki-ov-state: not_found # No ROAs found, or RPKI validation not enabled for source