Apply a custom WooCommerce order status based on user role

You can use folloeing code to register you custm status and change it when specific user ordered the product:

    function register_awaiting_shipment_order_status() {
register_post_status( 'wc-pendingwholesale', array(
    'label'                     => 'Awaiting shipment',
    'public'                    => true,
    'exclude_from_search'       => false,
    'show_in_admin_all_list'    => true,
    'show_in_admin_status_list' => true,
    'label_count'               => _n_noop( 'Awaiting shipment <span class="count">(%s)</span>', 'Awaiting shipment <span class="count">(%s)</span>' ),
) );
    }
    add_action( 'init', 'register_awaiting_shipment_order_status' );

   // Add to list of WC Order statuses
   function add_awaiting_shipment_to_order_statuses( $order_statuses )        {
$new_order_statuses = array();
// add new order status after processing
foreach ( $order_statuses as $key => $status ) {
    $new_order_statuses[ $key ] = $status;
    $new_order_statuses['wc-pendingwholesale'] = 'Awaiting shipment';
}

return $new_order_statuses;
  }
  add_filter( 'wc_order_statuses', 'add_awaiting_shipment_to_order_statuses' );

  add_action( 'woocommerce_order_status_changed', 'status_changed_processsing_weighted' );
  function status_changed_processsing_weighted( $order_id, $checkout = null ) {
  global $woocommerce;
  $order = new WC_Order( $order_id );

  $usermeta = get_user_meta( get_current_user_id() ,'wp_capabilities' ,true );
  if ( key( $usermeta ) === 'wholesale_customer' ) {
        $order->update_status( 'pendingwholesale', 'order_note' );
  }
 }