<?php
function woo_add_cart_fee() {

	global $woocommerce;

	$current_user = wp_get_current_user();

	if  ( in_array( 'residential', $current_user->roles, true) ) {

		$woocommerce->cart->add_fee( __( 'Custom', 'woocommerce' ), 5 );

	}

}
add_action( 'woocommerce_cart_calculate_fees', 'woo_add_cart_fee' );