get session data

[eluser]Aspi[/eluser]
Hi!

I would like get data from session.
I take session data into mysql;
Create table like this:

Code:

CREATE TABLE IF NOT EXISTS  `ci_sessions` (
session_id varchar(40) DEFAULT '0' NOT NULL,
ip_address varchar(16) DEFAULT '0' NOT NULL,
user_agent varchar(50) NOT NULL,
last_activity int(10) unsigned DEFAULT 0 NOT NULL,
user_data text DEFAULT '' NOT NULL,
PRIMARY KEY (session_id)
);

and put custom user data like this:

Code:

$newdata = array(
                   'username'  => $data['username'],
                   'roles' => $data['roles'],
                   'logged_in' => TRUE
               );

i would like get user_data->roles information

thanks for your help