Make this a 20 minute meal by microwaving the squash rather than roasting. Follow the same preparation and microwave for 10-12 minutes or until very soft.
Preheat oven to 400F. Cut acorn squash in half and remove seeds. Line a baking sheet with parchment paper or use glass bakeware to roast squash, cut side down, for 40 mins until very soft and easily pierced with a knife. Cool slightly, remove and transfer flesh into a bowl and process with a hand blender or whisk until smooth.
While squash is roasting, heat butter over medium heat. Once it starts to foam, reduce heat to medium-low and swirl the pan constantly until butter solids begin to lightly brown. Once butter is a light caramel colour, add sage leaves and continue to swirl while they sizzle for about 30 seconds. Remove sage with a slotted spoon and transfer to a paper towel to drain and crisp up. Add remaining browed butter to pureed squash. Season with salt and pepper to taste.
Cook pasta per package directions, ensuring the water is salted. Before draining water, reserve 1½ cups of the starchy pasta water.
Return drained pasta to pot. Add squash, parmesan cheese and a ½ cup of pasta water. Stir until well combined. Add more pasta water to thin sauce out and coat pasta as needed (you may not use it all). Season with additional salt and pepper to taste.