Roasted Vegetable Casserole   Ingredients: Extra-virgin olive oil, for drizzling 3 Yukon Gold potatoes, peeled and sliced 1/4 inch thick Salt ground pepper 1 small onion, thinly sliced 3lgarlic clove, minced 1 teaspoon thyme leaves 3 tomatoes, sliced 1/4 inch thick 2 small zucchini (1/2 pound), sliced 1/4 inch thick …