1. Preheat the oven to 220°C (425°F).
2. Line a baking sheet with parchment paper.
3. Peel the squash, remove the seeds, and cut it into thin slices.
4. Place the squash slices in a bowl. Drizzle olive oil over them while stirring until the slices are well coated. Season with salt and pepper to taste.
5. Spread the squash slices on the baking sheet.
6. Bake for 15 minutes, flipping the squash slices halfway through. They should be golden and roasted by the end of cooking.
7. Meanwhile, cook the spaghetti in a pot of salted boiling water according to the package instructions.
8. Cut the bacon into thin pieces. Grill them in a non-stick skillet.
9. Clean and pat dry the sage leaves.
10. When the spaghetti is cooked, drain it and transfer it to a dish.
11. When the squash slices are roasted, remove them from the oven and add them to the spaghetti. Also, add the grilled bacon pieces, grated Parmesan cheese, and sage leaves. Season with salt and pepper to taste, if needed, then mix well.
12. Serve immediately on plates.
13. Enjoy while hot.