Preheat the oven to 400°F.
Place the cauliflower florets on a baking sheet and toss with 3 tablespoons of the oil and season with salt and pepper.
Roast until the cauliflower is nicely colored and tender when pierced with a sharp knife, 20 to 30 minutes.
Remove the cauliflower from the oven and increase the oven temperature to 550°F. Toss the cauliflower with the curry powder until evenly coated.
Shape the pizza crust. Brush the dough evenly with the remaining 1 tablespoon oil, leaving about a 1-inch border all around.
Scatter the red onion over the crust followed by the tomatoes. Spread the curried cauliflower over the onion and tomatoes. Sprinkle with the pepper flakes.
Transfer the pizza to the oven and bake until the crust is browned, the tomatoes have softened, and the onions are just coloring, 6 to 10 minutes. To serve, scatter the cilantro over the top of the pizza.