Preheat the oven to 400°F. Line a rimmed baking sheet with foil.
Put the bacon in a medium skillet and cook over medium heat until the fat has rendered and the bacon is very crispy. Remove the bacon with a slotted spoon and drain on paper towels. Reserve 1 tablespoon of bacon fat.
Toss the Brussels sprouts with the reserved bacon fat, olive oil, salt, and pepper. Place on the baking sheet in an even layer. Roast for 20 minutes. Pour the maple syrup over the sprouts, stir to coat, and roast for another 5 minutes or until the sprouts are crispy and browned on the outside and tender on the inside.
Add the diced bacon to the Brussels sprouts, toss lightly to combine, and serve.