Preheat the oven to 425°F (220°C). In a large mixing bowl, toss together diced zucchini, eggplant, red and yellow bell peppers, and red onion with olive oil, dried Italian herbs, salt, and black pepper. Spread these vegetables evenly on a baking sheet and roast for 20-25 minutes, stirring once halfway through, until they are caramelized and fork-tender with a nice golden color.

While the vegetables are roasting, prepare the béchamel sauce. In a medium saucepan, melt 4 tablespoons of unsalted butter over medium heat. Whisk in ¼ cup of all-purpose flour, cooking for 1-2 minutes until bubbly. Gradually add in 3 cups of warmed whole milk, whisking continuously until the mixture thickens, resembling a creamy consistency. Stir in a pinch of ground nutmeg, salt, white pepper, and ½ cup of grated Parmesan cheese until smooth and glossy.

In a rectangular baking dish, start layering your ingredients for the Roasted Vegetable Lasagna. Begin with a layer of roasted vegetables, followed by a thin layer of béchamel sauce, and then place a layer of no-boil lasagna noodles. Repeat the layering process until all ingredients are used, ensuring the last layer is béchamel sauce topped with a generous sprinkle of shredded mozzarella cheese for a deliciously cheesy finish.

Cover the assembled lasagna with foil to lock in moisture and bake in the preheated oven at 375°F (190°C) for 25 minutes. After this time, carefully remove the foil and continue baking for an additional 15 minutes. The top should be bubbly and golden brown, with the edges slightly crisped for that perfect texture.

Once done, remove the lasagna from the oven and let it rest for about 10 minutes. This allows the layers to set and makes slicing easier. Garnish your Roasted Vegetable Lasagna with fresh basil leaves, adding a pop of color and flavor before serving. Enjoy this comforting homemade meal with friends or family!