Step 1: Preheat your oven to 400°F (200°C). Toss the cubed butternut squash with olive oil, nutmeg, salt, and pepper. Roast for 25-30 minutes until tender and caramelized.
Step 2: While the squash roasts, make the bechamel sauce by melting butter in a saucepan. Whisk in flour and cook for 2 minutes. Gradually whisk in milk until the sauce thickens. Season with salt, pepper, and minced sage.
Step 3: In a small bowl, combine the ricotta with half of the Parmesan cheese. Mash half of the roasted butternut squash and fold it into the ricotta mixture for a creamy autumn vegetable lasagna with butternut squash filling.
Step 4: Spread a thin layer of bechamel at the bottom of a 9x13 inch baking dish. Place a layer of noodles on top.
Step 5: Spread a portion of the ricotta-squash mixture, followed by some whole roasted squash cubes, mozzarella, and a drizzle of bechamel. Repeat layers until ingredients are used, ending with noodles, bechamel, and the remaining Parmesan and mozzarella.
Step 6: Cover with foil and bake at 375°F (190°C) for 30 minutes. Remove foil and bake for another 15-20 minutes until the top of the autumn vegetable lasagna with butternut squash is golden and bubbly.
Step 7: Let the autumn vegetable lasagna with butternut squash rest for 10 minutes before slicing and serving.