Adjust oven rack to upper position, place a foil-lined rimmed baking sheet on it, and preheat oven to 500°F (260°C). Toss sprouts with olive oil and season to taste with salt and pepper. Remove baking sheet from oven and add brussels sprouts, working quickly to turn them all cut-side-down. Return to oven and roast until tender and deeply browned, about 20 minutes total. Serve immediately