Preheat your oven to 425°F (220°C). Toss the diced butternut squash in a large bowl with olive oil, salt, and black pepper until evenly coated. Spread the squash in a single layer on a baking sheet, roasting it for 25-30 minutes.

While the squash roasts, bring a large pot of salted water to a rolling boil. Add the rigatoni or your choice of short pasta, cooking according to the package instructions until al dente, usually about 8-10 minutes. Reserve about 1 cup of the pasta water before draining.

In a large skillet, melt the unsalted butter over medium heat, stirring frequently. Add the fresh sage leaves and cook for about 4-5 minutes until the butter is nutty brown, crisping the sage leaves.

Remove the crispy sage from the skillet and set aside. Add the minced garlic and optional red pepper flakes to the browned butter, sautéing for about 30 seconds. Stir in the roasted butternut squash for another 2-3 minutes.

Add the drained pasta to the skillet and sprinkle in the grated Parmesan cheese. Gradually mix in the reserved pasta water to achieve your desired creaminess, tossing gently until well combined.

Serve while hot, garnishing each serving with crispy sage leaves, additional Parmesan cheese, and a drizzle of olive oil if desired.