Preheat your oven to 400°F (200°C).
Toss the cubed butternut squash in 1 tablespoon of olive oil, salt, and pepper. Spread on a baking sheet and roast for 25-30 minutes.
Meanwhile, cook the pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the remaining tablespoon of olive oil over medium heat. Add the diced onion and garlic, sauté until translucent.
Add the Italian sausage to the skillet. Break it apart and cook until browned and cooked through.
Stir in the roasted butternut squash, spinach, and rosemary into the skillet, cooking until the spinach wilts.
Add the cooked pasta to the skillet and toss everything together. Sprinkle in the Parmesan cheese and mix until melted.
Season with salt and pepper to taste, then serve warm.