Preheat the oven to 450°F. Line a rimmed baking sheet with parchment paper.
Cut each squash half into several wedges, then halve the wedges crosswise.
On the prepared baking sheet, toss the squash with oil and chili powder; season with salt and pepper, and toss again. Roast until tender and starting to brown, 20 to 25 minutes, tossing halfway through. Drizzle with melted butter, for serving.