Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper for easy cleanup (optional).
Carefully peel the butternut squash with a sharp knife. Cut it in half lengthwise, scoop out the seeds, and then dice the flesh into 1-inch cubes.
In a mixing bowl, combine the olive oil, brown sugar, cinnamon, salt, and black pepper.
Add the diced butternut squash to the bowl and toss until the pieces are evenly coated with the mixture.
Spread the coated squash in a single layer on the prepared baking sheet.
Roast in the preheated oven for about 30 minutes, or until the squash is tender and lightly caramelized, stirring halfway through the cooking time for even roasting.
Once done, remove from the oven and let cool for a few minutes. If desired, sprinkle with chopped pecans or walnuts before serving.