Whisk together the curry powder, cumin, salt, pepper and olive oil in a medium bowl.
Spread the cauliflower, carrots, and onion in a single layer on a large baking sheet-lined with tin foil. Drizzle with the dressing and toss so it is thoroughly coated.
Roast the vegetables in the oven until tender and browned, about 40 minutes, stirring halfway through cooking. Remove to a serving bowl and sprinkle with parsley and a drizzle of olive oil on top. Serve hot or at room temperature.