get session data

[eluser]Aspi[/eluser]
THX everybody help

i try $roles = $this->session->userdata('roles'); nothing happen
and i try $roles = $this->session->userdata('user_data'); nothing happen

if i try $roles = $this->session->userdata('session_id'); show session id

is very frustrating userdata('roles') don't return any information.

and another question is i must unserialize userdata('roles') ?

THX