Cook the rice according to pack instructions then drain and leave to cool.
Meanwhile, preheat the oven to 200°C, gas mark 6. Whisk together 1 tbsp olive oil and the honey, then season. Tip the Brussels sprouts onto a baking tray, pour over the honey and oil and turn to coat. Roast for 25 minutes until the edges are crisp. Remove from the oven and keep warm.
Put the cooked wild rice and sprouts in a large bowl. Add the cranberries, onion, cabbage, herbs, chestnuts and radishes. Drizzle with the remaining olive oil, season and stir in the lemon juice. Toss to coat and serve immediately.