Preheat the oven to 400°F (200°C).
Peel, seed, and cube the butternut squash. Toss with olive oil, salt, and pepper. Spread on a baking sheet.
Roast the butternut squash in the oven for 25-30 minutes, or until tender and lightly browned.
While the squash is roasting, cook the lasagna noodles according to package instructions until al dente. Drain and set aside.
In a large bowl, combine ricotta cheese, spinach, minced garlic, and oregano. Mix well and season with salt and pepper.
Once the squash is roasted, add it to the ricotta mixture and stir to combine.
Spread a thin layer of marinara sauce on the bottom of a 9x13 inch baking dish.
Layer noodles, followed by the ricotta-squash mixture, mozzarella, and more marinara. Repeat until all ingredients are used, finishing with noodles and sauce on top.
Sprinkle grated Parmesan cheese over the top layer of sauce.
Cover with foil and bake for 25 minutes. Then remove the foil and bake for an additional 15-20 minutes until bubbly and golden.
Allow the lasagna to rest for 10-15 minutes before slicing and serving.