1. Preheat oven to 375°F (190°C).
2. Toss butternut squash with olive oil, salt, and pepper. Roast for 25-30 minutes until tender.
3. In a saucepan, melt butter and add flour to make a roux. Slowly whisk in milk, add nutmeg, and cook until thickened.
4. In a mixing bowl, combine ricotta, sage, and garlic. Season with salt and pepper.
5. In a baking dish, layer lasagna noodles, ricotta mixture, roasted squash, mozzarella, and Parmesan. Repeat layers.
6. Pour milk sauce over the top and sprinkle with remaining mozzarella and Parmesan.
7. Cover with foil and bake for 30 minutes. Remove foil and bake for an additional 15 minutes until golden and bubbly.
8. Let rest for 10 minutes before serving.