Display User Role Next To Comment

Just pass the user id to this function:

function get_role($user_id)
{
    if(is_int($user_id))
    {
        $user = new WP_User( $user_id );
        if ( !empty( $user->roles ) && is_array( $user->roles ) ) 
        {
            foreach ( $user->roles as $role )
                echo $role;
        }
    }
    else
        echo "Something else";
}