Preheat oven to 350°. Toast walnuts on baking sheet for 8–10 minutes, stirring halfway through. Remove and cool to room temperature. Increase oven temperature to 425°.
Slice large sprouts in half, if needed, so all are about the same size. Toss sprouts in large bowl with remaining ingredients. Spread on rimmed baking sheet in even layer.
Roast for 25–30 minutes, stirring halfway through, or until browned and tender. Toss with toasted walnuts, and serve warm.