Preheat oven to 200°C fan forced. Lightly grease two roasting pans. Arrange the radicchio in 1 roasting pan. Drizzle over 1 tablespoon of oil, season and turn to coat. Set aside.
Add fennel to the second roasting pan. Combine maple syrup and remaining oil, spoon over the fennel, turning to coat. Season well. Roast for 25-30 minutes, turning once, or until fennel is golden and tender. Set aside.
Place the pan with Treviso¢ radicchio into the oven, roast for 15-20 minutes, turning after 10 minutes. Scatter the walnuts over a baking tray, place into the oven under the radicchio and cook for 5-8 minutes until toasted.
Arrange the radicchio on a board or serving platter. Top with fennel, oranges, walnuts and parsley. Whisk all the dressing ingredients together and spoon over the salad just before serving.