How to associate roles and users？

[lynliuyan]

role root uG
role_transitions admin
subject /
/
/opt rx
/home rwxcd
/mnt rw
/bin rx
/sbin rx
/lib rx
/lib32 rx
/libx32 rx
/lib64 rx
/usr rx
$grsec_denied
......

role test u
subject /
/
/opt rx
/home rwxcd
/mnt rw
$grsec_denied
......

why the system user root or test login, the roles is default?