Preheat oven to 220°C (425°F/Gas Mark 7). Remove outer leaves from cauliflower and trim stem, leaving head intact so that cauliflower will sit flat. Place cauliflower in large microwave-safe bowl and add water. Microwave on HIGH for 10 minutes. Transfer cauliflower to foil-lined baking pan.
Mix melted butter and Buffalo Wings Sauce in small bowl. Brush cauliflower with mixture, making sure to brush into crevices and between florets.
Roast 30 to 35 minutes or until nicely browned.
Meanwhile, place shredded cheeses in large bowl. Add corn starch and toss until cheese is coated. Bring wine to simmer in small saucepan. Gradually add cheese, stirring constantly until melted and smooth. Remove from heat, stir in the garlic powder and mustard.
Transfer cauliflower to serving platter. Pour half of the hot cheese fondue mixture over the cauliflower. Drizzle with additional Buffalo Wings Sauce. Place remaining fondue in small serving bowl. Cut roasted cauliflower into bite-size pieces and serve with remaining fondue cheese for dipping.