Preheat the oven to 450 degrees F. Lightly spray a nonstick baking sheet with cooking spray.
In a large bowl, whisk together the rice flour, garlic powder, cumin, paprika, salt and pepper. Whisk in 1 cup water until completely incorporated and you have a thin batter. Add the cauliflower florets and toss to coat completely with the batter. Use tongs or a fork to remove the florets from the bowl, allowing excess batter to drip off. Place in a single layer on the prepared baking sheet.
Bake until the batter begins to set, about 10 minutes. Use tongs or a spatula to flip the florets and bake the other side until the batter looks completely dry, about 10 minutes longer.
Meanwhile, combine the barbecue sauce and butter in a small saucepan. Cook over medium heat, stirring occasionally, until the butter is melted.
When the cauliflower is done, use a pastry brush to completely coat the florets with the sauce. Bake again until the florets are crispy and the sauce is completely absorbed, 8 to 10 minutes. Serve with carrot and celery sticks on the side.
Substitute wing sauce for barbecue sauce and you can serve Buffalo cauliflower wings!