1. To make the sauce, position an oven rack in the top third of the oven and preheat the oven to 450°. Line a large rimmed baking sheet, such as a 12 x 17-inch "half sheet" pan, with aluminum foil, and oil the foil with some olive oil.

2. Arrange the tomatoes, red bell pepper, onion, zucchini, and jalapeño, cut sides up, on the pan. Brush with about 3 tablespoons olive oil. Season with salt and pepper to taste. Place the garlic, cut sides down, on the pan. Roast until the vegetables are tender and the edges are beginning to brown, about 30 minutes.

3. Cool until the vegetables are easy to handle. Remove the tomato skins and seeds from the tomato flesh and reserve both in a bowl. Strain the tomato skins and seeds in a wire sieve, pressing hard on them to remove the juices. Combine the tomatoes, strained juices, red pepper, onion, and jalapeño in a food processor. Squeeze in the garlic flesh from the hulls. Add the basil and oregano. Pulse to make a coarsely chopped sauce. Season with salt and pepper. (The sauce can be made up to 2 days ahead, cooled, covered, and refrigerated.) Transfer to a saucepan. Cook over medium heat until simmering. Keep warm.

4. Meanwhile, bring a large pot of lightly salted water to a boil over high heat. Add the spaghetti and cook according to the package instructions. Drain well. Return the pasta to the warm cooking pot, add the sauce, and mix well.

5. Serve hot in individual bowls, with a bowl of Parmesan passed at the table.