Preheat oven to 425°F.
Combine curry powder, paprika, cumin, salt, and pepper in a bowl. Spread cauliflower and chickpeas out on two separate rimmed baking sheets. Toss cauliflower with 2 Tbsp. of the oil, and chickpeas with remaining 1 Tbsp. oil. Sprinkle 1 Tbsp. of the spice mixture over chickpeas, and toss to coat. Sprinkle remaining spice mixture over cauliflower, and toss to coat. Place both baking sheets in the oven, and set timer for 30 minutes. After 15 minutes, shake the pan of chickpeas, and give the cauliflower a good toss. Remove chickpeas from the oven when the timer goes off, and let the cauliflower go 5 minutes longer.
Meanwhile, prepare Green Tahini Sauce by combining all ingredients in a blender or mini food processor. With motor running, gradually stream in 1/3 cup warm water and blend until smooth.
Prepare bowls by placing 1/2 cup cooked rice in each of 4 bowls. Divide roasted cauliflower and chickpeas evenly over each bowl, and drizzle Green Tahini Sauce overtop. Add additional garnishes (cucumber, tomatoes, avocado, additional herbs, etc.), if desired.