Preheat the oven to 400°F with a rack in the center position. Line a rimmed sheet pan with parchment paper.

In a small bowl, combine the butter, chili powder, cumin, salt, and brown sugar. Brush the cut sides of the squash with the butter mixture. Reserve any remaining butter in the bowl. Place the squash wedges, with one flesh side down, on the prepared sheet. Roast for 20 minutes. Remove the sheet pan from the oven. Tip the squash so that the other side of the flesh is touching the sheet pan and roast for 15 minutes more.

Remove from the sheet from the oven and flip the squash skin side down. Spoon reserved butter mixture over it. Return squash to the oven, and continue baking until tender, browned and caramelized, 15 minutes.