Bake zucchini and garlic on a rimmed cookie sheet at 450° for 12 minutes, stirring halfway through. Repeat procedure with bell peppers and onion. Reduce oven temperature to 350°. Toss together veggies and salt in a bowl. Stir together ricotta cheese, egg, 1½ cups of mozzarella cheese, and ¼ cup of grated Parmesan cheese.

Spread 1 cup of marinara on the bottom of a 13x9 baking dish coated with cooking spray. Top with 3 noodles, 1 cup sauce, 1/3 ricotta mixture and 1/3 of vegetable mixture. Repeat layers twice, beginning with 3 noodles. Top with remaining noodles and 1 cup sauce. Sprinkle with remaining ½+ cup mozzarella cheese and ¼ cup 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.