Preheat the oven to 400 F and line a large baking sheet with aluminum foil.
Separate the head of cauliflower into florets of roughly equal size.
Drain, rinse, and dry the chickpeas with paper towels.
In a small bowl, whisk together the olive oil, cumin, coriander, cayenne and garlic powder and salt.
Toss the cauliflower with 2/3 of the spice mixture in a medium bowl.
Toss the chickpeas with the remaining spice mixture in a small bowl.
Spread the cauliflower on one half of the prepared baking sheet, and the chickpeas on the other half.*
Roast in the preheated oven for about 30 minutes until cauliflower is tender and caramelized and chickpeas are crunchy, gently tossing them once, after about 15 minutes.
Tahini Dressing
While the cauliflower and chickpeas are roasting, in a small bowl, whisk together the tahini, lemon juice, olive oil, dijon, honey, garlic, and salt. Slowly whisk in the water until the desired consistency is reached.
To Serve
Divide arugula between 4 bowls. Top each bed of arugula with chickpeas and cauliflower. Drizzle with tahini dressing, and sprinkle with pomegranate seeds.
Notes
*I separate the chickpeas and cauliflower on the baking sheet because I find the chickpeas get crunchier that way, but you can toss them together with all of the spice mixture and roast together if you want to keep it simple.