Preheat the oven to 400 degrees. Prep the brussels sprouts by removing the outer leaves, cutting the stem end off, and slicing them lengthwise.
Place all of the brussels sprouts on a large baking sheet, then add the olive oil and balsamic vinegar. Season with a pinch of salt and pepper, then toss everything together to coat.
Roast for 20 minutes, then add the chopped pecans and toss together. Roast for another 5-10 minutes, until the brussles are turning brown, and the pecans are slightly toasted.
When done roasting, remove from the oven and transfer to a serving bowl. Add the cranberries, toss, and serve!