Heat the oven to 425 degrees. Lightly coat a 9 x 13 inch baking dish with olive oil.

Combine the zucchini, eggplant, onion, and garlic in a large roasting pan. Pour 1/4 cup olive oil over the vegetables and toss to coat them thoroughly. Season with 1 teaspoon salt and a generous grinding of pepper. Roast the vegetables, stirring them every 15 minutes, for 45 minutes, or until they are tender and nicely browned in spots. Scrape the vegetables into a large mixing bowl.

Reduce oven heat to 400 degrees.

While the vegetables are roasting, bring a large pot of water to a boil over high heat and salt generously. Add the pasta, stir to separate, and cook according to the manufacturer's instructions until not quite al dente. (It should be slightly underdone, because it will finish cooking in the oven.) Drain the pasta in a colander, reserving about 1 cup of the cooking water.

Put the tomatoes in a medium bowl and mix in the lemon juice, 1/2 teaspoon salt, and 2 tablespoons olive oil.

Transfer the pasta to a large bowl and toss with the roasted vegetables, the sausage, if using, and the roasted mushrooms. Add 2 cups of the tomato-lemon mixture and gently toss to combine thoroughly.

Spoon half of the pasta mixture into the prepared baking dish. Spread half of the sliced scamorza over the pasta. Spoon the remaining pasta on top, and cover with the remaining scamorza. Spoon the remaining tomatoes over the scamorza. Sprinkle the Parmigiano on top.

Cover the dish with foil and bake for 20 minutes; uncover and bake 20 minutes more, until the cheese is melted and bubbly and the top is nicely browned and crisp around the edges. Let stand for 5 minutes before serving.