Hide a shipping method based on a use role

functions.php

function wc_ninja_role_base_shipping_method( $rates, $package ) {
	// Make sure flat rate is available
	if ( isset( $rates['flat_rate'] ) && ! current_user_can( 'wholesale' ) ) {
		unset($rates['flat_rate']);
	}

	return $rates;
}
add_filter( 'woocommerce_package_rates', 'wc_ninja_role_base_shipping_method', 10, 2 );