Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper.
Place the halved Brussels sprouts in a mixing bowl. Add the olive oil, salt, black pepper, and chili flakes. Toss until the sprouts are evenly coated.
Spread the Brussels sprouts in a single layer on the prepared baking sheet. Scatter the diced bacon over and around them.
Roast for 20 to 25 minutes, stirring once halfway through, until the sprouts are browned and crisp at the edges and the bacon is cooked.
Remove the pan from the oven. Drizzle the maple syrup over the hot sprouts and bacon. Toss gently to coat.