Place oven rack in center and preheat to 425, then line a baking sheet with parchment paper
In a small bowl, mix together cumin, coriander, cayenne, salt and pepper.
Gently cut the florets from the cauliflower core and if needed trim them to fairly even-sized pieces.
Place the cauliflower and chickpeas onto the baking sheet, drizzle olive oil over them evenly and mix by hand to coat. Then sprinkle the spice mixture over the vegetables and gently mix by hand to distribute the spices.
Bake at 425 degrees for 15 minutes, then flip the cauliflower pieces with a spatula and cook another 10 minutes. If more browning is desired, broil for 2-3 minutes being careful not to burn the cauliflower.
For The Yogurt Sauce:
Combine yogurt, garlic, and cilantro in a small bowl and mix well.
Serve the cauliflower while still warm. Top with yogurt sauce and garnish with cilantro.