1. Preheat oven to 450 degrees. In a large bowl, whisk oil, syrup, salt, and pepper to blend. Trim brussels sprouts at base and remove any leathery outer leaves. Toss sprouts in oil mixture to coat well. Line a rimmed baking pan with foil and put sprouts in pan in a single layer.
2. Roast, tossing every 5 minutes, until sprouts are browned but tender-crisp, 10 to 12 minutes total. Remove from oven and let cool 10 minutes
3. Meanwhile, cut each prosciutto slice into strips about 1 in. wide. Gently wrap each sprout lengthwise in a prosciutto strip. Insert a toothpick into the base of each sprout. Serve at room temperature.

Make ahead: Prepare through step 2 up to 1 day ahead; chill, covered. Bring to room temperature, then proceed.