Preheat your oven to 400°F (200°C). Toss the cubed butternut squash with 1 tablespoon of olive oil, 1/2 teaspoon of salt, and 1/4 teaspoon of pepper on a baking sheet. Roast for 25 to 30 minutes, or until the squash is tender and lightly browned.
While the squash roasts, cook the pasta according to package directions until al dente. Reserve about 1 cup of the starchy pasta water before draining.
Return the sauce to the skillet over low heat. Stir in the Parmesan cheese, if using.
Add the drained pasta to the skillet with the sauce. Toss everything together until the pasta is fully coated. Add more reserved pasta water, a tablespoon at a time, if the sauce thickens too much.
Stir in the fresh sage, if using. Serve immediately for a cozy vegetarian dinner.
Notes
For a richer flavor, roast the squash with a pinch of smoked paprika.