Preheat oven to 425 degrees F (220 degrees C). Cut cauliflower into florets and slice carrots into rounds, keeping pieces roughly the same size. Line a rimmed baking sheet with parchment paper and spray with oil. Spread cauliflower and carrots in a single layer, drizzle with 2 tablespoons olive oil, and sprinkle with garlic powder, oregano, paprika, cumin, salt, and pepper. Toss to coat evenly. Roast for 25 to 30 minutes.

At the same time, drain and rinse the chickpeas and pat completely dry with a paper towel. Discard any loose skins. Wet chickpeas will steam rather than crisp, so dry them well. Toss in a bowl with 2 tablespoons olive oil, cumin, paprika, garlic powder, salt, and pepper. Spread on one half of a second lined baking sheet. Place diced sweet potatoes on the other half and drizzle with oil, salt, and pepper. Roast on the middle rack for 20 to 28 minutes until chickpeas are golden and sweet potatoes are fork-tender.

While everything roasts, make the tahini yogurt sauce. Add Greek yogurt, tahini, lemon juice, olive oil, garlic, cumin, and salt to a blender or food processor. Blend for about 60 seconds until smooth. Add water one tablespoon at a time if you prefer a thinner consistency. Taste and adjust salt or lemon.

After the first roasting round, remove the cauliflower and carrots tray. Squeeze fresh lemon juice over the top and scatter the parsley. Return to the oven for another 5 to 10 minutes until the edges are golden brown and slightly crispy. Watch carefully as cauliflower can burn quickly at this temperature.

To assemble, spoon a generous amount of tahini yogurt sauce onto the base of each bowl. Layer arugula or greens on top, then add the sweet potatoes, roasted cauliflower and carrots, and crispy chickpeas. Add toppings of choice and a squeeze of fresh lemon. Serve immediately.