Preheat the oven to 400°F.
In a large bowl, toss the squash with 1 tbsp EVO oil, salt, and pepper.Arrange in a single layer on a baking sheet lined with baking paper. Roast, stirring occasionally, until squash is golden and tender, 25-30 minutes. In the meantime, pour a tablespoon of olive oil into a pan for 30 seconds or until it is hot enough to add the sliced mushrooms. Stir them for about 15 minutes until they are crispy and brown. Season with salt and pepper.
When the mushrooms are ready, add the butternut squash to the pan, toss all together and remove from the heat. Set aside.
Heat the remaining 2 tablespoons of oil in a pan over medium-high heat. Working in batches, add sage leaves and cook until edges begin to curl and turn dark green, 1-2 minutes. Using a slotted spoon, carefully transfer to paper towels to drain.
Bring to boil a large pot of water. Add salt and cook the pasta according to the packet instructions. Ideally, remove the pasta 1 minute before finishing the cooking process. When the pasta is ready, take it out of the pot using a spaghetti spoon. Never drain long shaped pasta; it needs to retain some of the cooking water to let the sauce adhere better.Save ½ cup of starchy water for the sauce. While the pasta is cooking, combine the ricotta, nutmeg, ¾ tbsp of starchy water (you might need a bit more), and salt in a small bowl; stir together until you have a smooth sauce with a consistency similar to heavy cream.
Add the sauce to the pan together with the butternut squash and mushrooms.
Add the pasta to the other ingredients in the pan stirring constantly for about a minute.
Place the pasta on a serving dish or indivisual plates and garnish with the sage leaves and, if you like, some grated cheese.
Your pasta is ready to be served.