Chickpea, cauliflower and tomato salad with sumac yogurt

Brush two heavy large sheet pans with oil. Toss the cauliflower with 3 tablespoons of the oil on one prepared sheet pan. Spread the cauliflower out into a single layer and season with salt and pepper. Toss the tomatoes with 1 tablespoon of the oil on the second prepared sheet pan and season with salt and pepper. Roast the cauliflower until tender and well-browned and the tomatoes until blistered in spots, stirring once, for about 30 minutes. Transfer the tomatoes to a plate to cool. Add the chickpeas and the remaining 1 tablespoon oil to the same pan and toss to coat. Sprinkle the chickpeas with the cumin seeds and Aleppo pepper and roast until lightly browned and fragrant, about 10 minutes. Cool completely. Combine the cauliflower, tomatoes, chickpeas and parsley in a large bowl and toss carefully just to blend. (The salad can be prepared ahead. Keep at cool room temperature of up to 6 hours or refrigerate overnight. Allow to warm to room temperature before serving.)