Adjust oven rack to lowest position and preheat oven to 425°F (218°C).
Trim both ends of each delicata squash. Stand one squash up on the larger cut side and, using a chef’s knife, slice it lengthwise, down through the center of the squash, creating two even halves. Use a soup spoon to scrape out and discard seeds and any fibrous flesh. Repeat with second squash.
Place all 4 squash halves cut-side down on a large cutting board. Cut each squash half crosswise into 1-inch-thick slices. Transfer slices to large bowl. Add melted butter, salt, and pepper, and toss to evenly coat squash slices.
Transfer squash slices to a rimmed baking sheet, arranging them around the perimeter of the sheet with an even amount of space between each slice. Roast until squash slices are golden brown on the bottom, about 12 minutes. Use kitchen tweezers or tongs to flip each slice. Rotate baking sheet 180 degrees, return it to oven, and continue to roast until second side is golden brown, about 10 minutes. Remove sheet from oven, transfer squash slices to a platter, and serve.
