function change_role_name() {
global $wp_roles;
if ( ! isset( $wp_roles ) )
$wp_roles = new WP_Roles();
$wp_roles->roles['wpcargo_employee']['name'] = 'WPCargo Branch Manager';
// you can also use this code
// $wp_roles->role_names['administrator'] = 'Owner';
//$wp_roles->roles['wpcargo_branch_manager']['name'] = 'WPCargo Employee';
}
add_action('init', 'change_role_name');