add_filter( 'woocommerce_variation_prices', 'custom_price', 10, 2 );

function custom_price($price, $product) {
    if (!is_user_logged_in()) return $price;

$user = wp_get_current_user();
 $roles = ( array ) $user->roles;
 return $roles;

    if ( $roles = 'Administrator' ){
            $price = $price * 0.5;
    }

    return $price;
}