Admin Console of HR.Net allows only to list users by their primary role. And secondary roles are in a shade.
To display all users that belong to a particular role (primary or secondary) you can use this bit of sql:
select ur.userid, rl.rolename from oc_roles r inner join oc_rolelanguages rl on r.roleid = rl.roleid inner join oc_userroles ur on ur.roleid = r.roleid where rl.rolename = 'Role Name'