Preheat oven to 400F. Line a large baking sheet with parchment paper.
CUT SQUASH: Using a sharp chef's knife, chop off the hard ends of the squash. Then, place the squash upright on one of the flat cut ends. Cut down the squash to slice it in half (lengthwise). Remove the seeds using a spoon. Place squash halves on the cutting board, face side down. Then, cut across the squash into 1/2-inch pieces.
Place squash slices into a large mixing bowl. Using your hands, toss in olive oil, garlic powder, thyme, half the parmesan (1/4 cup), salt, and pepper until well-combined.
Place tossed squash slices onto the baking sheet in a single layer. Transfer to oven and roast for 20-25 minutes, until lightly browned + fork-tender.
Meanwhile, heat butter in a small pan until completely melted and bubbling. Add chopped sage leaves and stir to fry for about 3-4 minutes. Remove from heat.
Plate squash and drizzle with sage butter. Add remaining 1/4 cup parmesan and adjust any seasonings to taste. Serve hot!