Preheat oven to 425°F. Line a large, rimmed baking sheet with parchment paper.
Add the Brussels sprouts to a large bowl. Drizzle with olive oil and sprinkle with salt and pepper. Toss until evenly coated.
Arrange the Brussels sprouts on the prepared baking sheet in a single layer, cut side down. Leave space between them so they roast instead of steam. Use two baking sheets if needed.
Roast for 20 to 25 minutes, or until fork-tender with deeply browned, caramelized edges.
While the Brussels sprouts roast, add the diced bacon to a large skillet over medium heat. Cook for 7 to 9 minutes, stirring occasionally, until crispy.
Using a slotted spoon, transfer the bacon to a paper towel-lined plate. Carefully discard all but about 1 teaspoon of the bacon drippings.
Remove the skillet from the heat. Carefully add the bourbon and balsamic vinegar. Return the skillet to medium heat, scraping up any browned bits from the bottom.
Add the maple syrup, brown sugar, and salt. Bring to a gentle simmer and cook for 4 to 6 minutes, stirring occasionally, until the glaze has reduced slightly and coats the back of a spoon. It will thicken a little more as it cools.
Remove the skillet from the heat. Stir in the butter until melted and smooth.
Add the roasted Brussels sprouts to the skillet. Toss until evenly coated with the glaze.
Fold in the crispy bacon and toasted pecans, reserving a little of each for garnish if desired.
Transfer to a serving dish. Sprinkle with the reserved bacon and pecans, if using. Serve immediately.