Preheat oven to 400°F (200°C) and line a baking sheet with parchment.
Toss chopped cauliflower with 2 tbsp buffalo sauce, a pinch of salt, and roast 8–10 minutes until just tender.
Mix roasted cauliflower, chicken (if using), cream cheese, cheese, remaining buffalo sauce, and pepper in a bowl.
Cut puff pastry into 12 squares, place 1–2 tbsp filling in center of each, fold into wonton shapes and seal edges with a little water.
Brush with beaten egg, arrange on sheet, spray lightly with oil, and bake 12–15 minutes until golden and puffed.
Serve warm with extra buffalo sauce or ranch for dipping.