I think we still recommend using *new* pg_dump to dump *old* server when
upgrading. If one tries that with today's pg_dump (8.1beta1) against
a 8.1devel server of 6 May, i.e., predating roles, one gets:
pg_dump: SQL command failed
pg_dump: Error message from server: ERROR: relation "pg_catalog.pg_roles" does not exist
pg_dump: The command was: SELECT tableoid, oid, nspname, (SELECT rolname FROM pg_catalog.pg_roles WHERE oid = nspowner)
asrolname, nspacl FROM pg_namespace
Cheers,
Patrick