Preheat your oven to 400°F (200°C). Halve the butternut squash and drizzle with olive oil. Wrap garlic in foil and place alongside squash. Roast for 30-40 minutes until squash is tender.

Bring a pot of salted water to a boil. Cook paccheri pasta for 1-2 minutes less than package instructions. Reserve 1.5 cups pasta water before draining.

In a Dutch oven, heat over medium-high. Cook sliced sausage until browned and crispy, about 5-7 minutes. Transfer to a plate.

In the same pot, reduce heat to medium. Add chopped onion and cook until translucent, about 4-5 minutes. Squeeze roasted garlic into pot, stir in red pepper flakes and tomato paste, cooking for another 2 minutes.

Scoop roasted squash flesh into the Dutch oven with the onion mixture. Mash together and gradually add reserved pasta water to create a creamy sauce.

Add cooked pasta and browned sausage to the Dutch oven. Mix to coat pasta with sauce. Stir in grated Parmesan until melted. Serve hot.