Preheat oven to 400F. Place the Brussels sprouts, pecan halves and cranberries on a sheet pan. Add the olive oil, salt and pepper and toss it all together in the pan. Spread everything out in one single layer.
Roast the Brussels sprouts for 20 to 30 minutes until they're tender and browned and the pecans are toasted. Toss once during roasting, about halfway through.
Remove from the oven and drizzle with balsamic vinegar, then toss again. Serve and enjoy!