Preheat an oven, then line two rimmed baking sheets with parchment paper. In a large mixing bowl, combine olive oil, tahini, tomato paste, fresh lemon juice, cornstarch, harissa paste, za’atar, Kosher salt, and ground cinnamon, then whisk well.
Add cauliflower florets and drained chickpeas, then toss to evenly coat. Transfer to the prepared baking sheets, ensuring everything is in an even single layer.
Roast until the cauliflower is tender, but a little bit charred and the chickpeas are crispy. If you used two sheet pans, rotate them half way through cook time.
Transfer the roasted cauliflower and chickpeas to a serving bowl, then drizzle with as much tahini as you like. Sprinkle with flaky sea salt to taste, then garnish with chopped cilantro. Serve immediately with lemon wedges!