Preheat oven to 400 degrees. Line a baking sheet with parchment paper.
In a large bowl, toss together butternut squash, 1 tablespoon olive oil, salt and pepper. Transfer to prepared baking sheet and cook for 25 minutes.
Cook pasta according to package directions.
Meanwhile, heat 1 tablespoon of oil in a skillet. Fry sage until crispy, about two minutes. Remove sage from skillet.
Add onion, garlic and red pepper flakes to the skillet. Season with salt and pepper and cook for 5 minutes
Add butter to the skillet and melt. Add cooked pasta and butternut squash and toss until coated. Transfer to serving plates and top with sage, parmesan and walnuts.