Preheat oven to 400 degrees F. Line a baking sheet with aluminum foil. Set aside.
Cut bacon into bite-sized pieces and place in a single layer on baking sheet. Bake for 13-15 minutes in preheated oven until crispy but not overcooked.
While bacon is cooking, cut sprouts in half lengthwise, then half them again to create quarters. Place in a bowl with balsamic vinegar, olive oil, salt and pepper. Toss to coat.
When bacon in done, transfer to paper towel-lined plate to drain. Arrange sprouts in a single layer on same baking sheet. Roast 20-30 minutes, turning sprouts every 10 minutes or so to help even cooking, until tender and browned.
Remove from oven and add bacon back to pan, arranging it evenly with sprouts. Sprinkle brown sugar over sprouts, if using, then return to oven and roast another 6-8 minutes until sugar is caramelized.