WooCommerce set tax exemption based on user role

functions.php

<?php
add_filter( 'init', 'wc_tax_exempt_user_roles' );
function wc_tax_exempt_user_roles() {
	if ( ! is_admin() ) {
		global $woocommerce;
		if ( current_user_can('wholesaler') || current_user_can('distributor') ) {
			$woocommerce->customer->set_is_vat_exempt(true);
		} else {
			$woocommerce->customer->set_is_vat_exempt(false);
		}
	}
}
?>

This snippet won't work in your use case. You should take a look into the tax classes instead and define rules based on them.