Preheat oven to 350°F. Lightly coat a 2-quart rectangular baking dish with nonstick cooking spray; set aside.
If using fresh asparagus, snap off and discard woody bases. If desired, scrape off scales. Cut into 1-inch-long pieces.
In a large saucepan bring about 1 inch water to boiling. Add asparagus, yellow sweet pepper strips, zucchini, and onion. Return just to boiling; reduce heat slightly. Cover and boil about 5 minutes or until crisp-tender. Drain well. Stir in roasted red sweet peppers. Spread asparagus-pepper mixture evenly in baking dish. Sprinkle with half of the mozzarella cheese.
In a large bowl whisk together egg product, milk, snipped or dried dill, salt, and black pepper until well mixed. Whisk in flour, making sure it is completely combined. Pour over vegetables in baking dish. Bake, uncovered, about 35 minutes or until slightly puffed and top shakes set. Sprinkle with remaining mozzarella cheese and Parmesan cheese. Let stand for 10 minutes before serving. If desired, garnish individual servings with dill sprigs.