Preheat oven to 450°. Bake zucchini, mushrooms, and garlic in a jelly-roll pan coated with cooking spray 12 to 14 minutes or until vegetables are crisp-tender, stirring halfway through. Repeat procedure with bell peppers and onion. Reduce oven temperature to 350°. Toss together vegetables and salt in a bowl.
Stir together ricotta, egg, 1 1/2 cups shredded mozzarella cheese, and 1/4 cup grated Parmesan cheese.
Spread 1 cup Basic Marinara Sauce in a 13- x 9-inch baking dish coated with cooking spray. Top with 3 noodles, 1 cup sauce, one-third of ricotta mixture, and one-third of vegetable mixture; repeat layers twice, beginning with 3 noodles. Top with remaining noodles and 1 cup sauce. Sprinkle with remaining 1/2 cup shredded mozzarella and 1/4 cup grated Parmesan.
Bake, covered, at 350° for 45 minutes. Uncover and bake 10 to 15 more minutes or until cheese is melted and golden. Let stand 10 minutes.