Roasted Chicken with butter

1 tablespoon unsalted butter 3 large leeks , sliced crosswise 1/4 inch thick and separated into rings (white and tender green portions only) 2 cups shredded[...]

1 (3 lb) whole chickens 12 medium red potatoes, trimmed around center 12 asparagus spears , trimmed, halved crosswise 3 carrots , cut into sticks olive oil[...]