Preheat your oven to 425 degrees Fahrenheit and set out a large rimmed baking sheet. If you do not have a large rimmed baking sheet, feel free to use two smaller rimmed baking sheets.
In a large bowl, toss together the brussels sprouts with the olive oil, salt, and pepper and transfer the sprouts onto the baking sheet. Spread them into a single layer and pop them into the oven for 25 to 30 minutes or until crisp and brown on the outside and tender on the inside, stirring about halfway through to encourage even browning.
Remove the pan from the oven and add on the balsamic vinegar and chopped dried cranberries and return the sprouts to the oven for five minutes.
Season the roasted sprouts with a little more salt and serve immediately.