Preheat oven to 450°F with a rack in the upper third of the oven. Trim and halve the Brussels sprouts, toss with oil, and roast, cut side down on baking sheet, for 20-35 minutes, depending on size and desired taste. They should brown but remain somewhat firm.
Meanwhile, stir together the ingredients for the dressing in a small bowl.
If making puffed rice, cook ingredients together in a small skillet until toasted and slightly browned.
When sprouts are done, transfer to a serving bowl and add just enough dressing to coat. Top with more chopped mint or cilantro, and puffed rice if using.
