Preheat oven to 425°F. Line a baking sheet with parchment paper.
Spread chopped cauliflower onto the baking sheet. Lightly oil and season with salt and pepper.
Roast for 20–25 minutes until tender and lightly browned. Allow to cool slightly.
Reduce oven temperature to 350°F.
In a large bowl, combine cream cheese, sour cream, mayonnaise, garlic powder, onion powder, Worcestershire sauce, buffalo sauce, cheddar cheese, and blue cheese. Mix until smooth.
Fold in shredded chicken, celery, and roasted cauliflower.
Transfer mixture to a greased baking dish. Top with additional cheddar cheese if desired.
Bake for 15–20 minutes until hot, melted, and bubbly.
Garnish with scallions and serve warm with chips, bread, crackers, or vegetables.