WooCommerce Customer Tax Exempt based on role

woocommerce_customer_role_tax_exempt.php

<?php
// Place the following code in your theme's functions.php file and replace tax_exempt_role with the name of the role to apply to
add_action( 'init', 'woocommerce_customer_tax_exempt' );
function woocommerce_customer_tax_exempt() {
    global $woocommerce;
    if ( is_user_logged_in() ) {
        $tax_exempt = current_user_can( 'tax_exempt_role');
        $woocommerce->customer->set_is_vat_exempt( $tax_exempt );
    }
}

This is great.

What do I do for multiple roles?

Also this seems to have worked on the front-end but creates a strange error when I try to go back to the admin area. I get this: http://i.imgur.com/nNHMSAZ.png

This broke my site when I made it a snippet. Do I just need to create the role first?