Heat oven 425 degrees. Toss the Brussels sprouts with olive oil and season with salt and pepper.
Spread the Brussels sprouts in one even layer in a sheet roasting pan. Roast about 20-25 minutes. The Brussels sprouts should be tender at the core and beginning to brown slightly around the edges.
In a small saucepan, heat butter with maple syrup until the butter is melted and the mixture is warm. Toss the Brussels sprouts with the butter-syrup mixture and return them to the oven for an additional 5-10 minutes of cooking.