Heat the oven: Heat the oven to 425°F. Line a large rimmed baking sheet with parchment paper.
Crisp the bacon: Cook the chopped bacon in a large skillet over medium heat, 8 to 10 minutes, until crisp. Lift it out with a slotted spoon and leave the rendered fat in the pan.
Toss the sprouts: Toss the halved sprouts with the olive oil, about 2 tablespoons of the bacon fat, salt, and pepper on the baking sheet. Spread them in a single layer, cut-side down, with space between them.
Roast the first round: Roast for 20 minutes, until the cut sides are deeply browned and the centers pierce easily with a fork.
Glaze and finish: Drizzle the maple syrup over the sprouts, scatter the crisp bacon on top, and return the pan to the oven for 5 to 8 minutes more, until the glaze is bubbling and the edges are caramelized. Watch closely during the last few minutes — maple syrup goes from caramelized to burnt fast.
Serve hot: Serve straight from the pan, while the edges are still crisp.