Make the marinade. Preheat an oven to 450°F (230°C), then line a rimmed baking sheet with parchment paper. In a large bowl, whisk together 1 cup buttermilk, ¼ cup flour, and 1 Tbsp hot sauce. Add the cauliflower florets, then gently toss to coat.
Coat the cauliflower. In a second bowl, combine 2 cups breadcrumbs, 1 tsp garlic powder, and 1 tsp onion salt, then mix well. Place cauliflower in the breadcrumb mixture, being sure to allow excess marinade to drip off before tossing on all sides. Transfer each piece of cauliflower to the prepared baking sheet, leaving a little room in between.
Roast the cauliflower. Cook for 30-35 minutes, or until the florets are golden brown. While the cauliflower is cooking, make the sauce.
Make the hot honey sauce. Combine 8 Tbsp (1 stick) unsalted butter, 2 Tbsp honey, 1½ tsp cayenne pepper, 1 tsp garlic powder, 1 tsp sweet paprika, ½ tsp chili powder, ½ tsp Kosher salt, and ¼ tsp black pepper in a saucepan. Heat over medium-high heat until the butter has melted and the spices become fragrant, stirring well.
Toss with the sauce. Pour the hot honey sauce on top of the cauliflower, then toss well until evenly coated. (For less spice, you can simply brush the hot sauce onto the tops of the cauliflower). Transfer to a large serving platter, then garnish with chopped parsley. Serve immediately with a Ranch or Blue Cheese dressing.