Change user role after purchase is successful. Need to expand this example to include conditional processing based on products purchased.

change_user_role_after_purchase.php

add_action('woocommerce_thankyou', 'mindsize_change_role_on_successful_purchase');

function mindsize_change_role_on_successful_purchase($order_id ) {
 $order = new WC_Order( $order_id );
 $user_id = $order->user_id;
 $wp_user_object = new WP_User($user_id);
 if($wp_user_object->roles[0] != "administrator"){ // Do not change admin role
  wp_update_user( array( 'ID' => $wp_user_object->ID, 'role' => "wholesale" ) );
 }
}