Looking for a list of role-user relationships.

I’ve done it, but cross joining with many function calls doesn’t feel ‘efficient’ to me ?

Does anyone know of a more efficient way ?

select 
u.usename,
r.role_name,
user_is_member_of(u.usename, r.role_name)
from SVV_ROLES r, pg_user u
where user_is_member_of(u.usename, r.role_name) = true