Hi Apple, 
I just made some modified lines in these files. Just add the modified lines into yours. 
Just see the comment "MY CUSTOM CODE FOR ROLE NAME"
I couldn't share whole file because too long and it will make you confuse to read those a lot of lines 
For current_user.inc (location at includes/current_user.inc)
class current_user
{
    var $user;
    var $loginname;
    var $username;
    var $name;
    var $company; // user's company
    var $pos;
    var $access;        
    var $timeout;
    var $last_act;
    var $role_set = false;
    var $old_db;
    var $logged;
    var $ui_mode = 0;
    
    var $prefs;
    var $cur_con; // current db connection (can be different from $company for superuser)
        
        /* custom */
        var $rolename; // MY CUSTOM CODE FOR ROLE NAME
        var $org_id;
    function current_user()
    {
        global $def_coy;
        
        $this->loginname = $this->username = $this->name = "";
        $this->company = isset($def_coy)? $def_coy : 0;
        $this->logged = false;
        $this->prefs = new user_prefs();
    }
    function logged_in()
    {
        return $this->logged;
    }
    function set_company($company)
    {
        $this->company = $company;
    }
    function login($company, $loginname, $password)
    {
        global $security_areas, $security_groups, $security_headings, $path_to_root;
        
        $this->set_company($company);
        $this->logged = false;
        $Auth_Result = get_user_for_login($loginname, $password);
        if (db_num_rows($Auth_Result) > 0)
        {
            $myrow = db_fetch($Auth_Result);
            $this->old_db = isset($myrow["full_access"]);
            if (! @$myrow["inactive"]) {
                if ($this->old_db) { 
                    // Transition code:
                    // db was not yet upgraded after source update to v.2.2
                    // give enough access for admin user to continue upgrade
                    if (!isset($security_groups) || !isset($security_headings)) {
                        echo "<center><br><br><font size='5' color='red'><b>";
                        echo _('Before software upgrade you have to include old $security_groups and $security_headings arrays from old config.php file to the new one.');
                        echo '<br>'."<a href=$path_to_root/index.php>"._("Back")."</a>";
                        echo "</b></font><br><br></center>";
                        exit;
                    }
                    $this->access = $myrow["full_access"];
                    if (in_array(20, $security_groups[$this->access]))
                        // temporary access for admin users
                        $this->role_set[] = $security_areas['SA_SOFTWAREUPGRADE'][0];
                    else {
                        echo "<center><br><br><font size='5' color='red'><b>";
                        echo _('System is available for site admin only until full database upgrade');
                        echo "</b></font><br><br></center>";
                        exit;
                    }
                } else {
                    $this->role_set = array();
                    $this->access = $myrow["role_id"];
                    // store area codes available for current user role
                    $role = get_security_role($this->access);
                    if (!$role) 
                        return false;
                    foreach( $role['areas'] as $code )
                        // filter only area codes for enabled security sections
                        if (in_array($code&~0xff, $role['sections'])) 
                            $this->role_set[] = $code;
                                                
                                         $this->rolename = $role['role'];  // MY CUSTOM CODE FOR ROLE NAME 
                }
                $this->name = $myrow["real_name"];
                $this->pos = $myrow["pos"];
                $this->org_id = $myrow["org_id"];
                $this->loginname = $loginname;
                $this->username = $this->loginname;
                $this->prefs = new user_prefs($myrow);
                $this->user = @$myrow["id"];
                update_user_visitdate($this->username);
                $this->logged = true;
                $this->last_act = time();
                $this->timeout = session_timeout();
            }
        }
        return $this->logged;
    }
        .....
        .....
For security_db.inc (location at admin/db/security_db.inc)
..........
function get_security_role($id)
{
    $sql = "SELECT * FROM ".TB_PREF."security_roles WHERE id=".(int)$id;
    $ret = db_query($sql, "could not retrieve security roles");
    $row = db_fetch($ret);
    if ($row != false) {
        $row['role'] = $row['role']; // MY CUSTOM CODE FOR ROLE NAME
        $row['areas'] = explode(';', $row['areas']);
        $row['sections'] = explode(';', $row['sections']);
    }
    return $row;
}
...................
renderer.php (location at themes/default/renderer.php)
..............
echo "<p id='user-info'>" . _("Welcome") . ", " . $_SESSION["wa_current_user"]->name .
       " (" . $_SESSION["wa_current_user"]->rolename . ")</p>";
..............
now I can access rolename via $_SESSION['wa_current_user']->rolename
Good luck brother
Feel free to ask me if you still need help 