Preheat oven to 400°F (200°C).
In a large bowl, toss sliced carrots and chickpeas with olive oil, harissa paste, cumin, smoked paprika, salt, and cinnamon (if using). Spread onto a lined baking sheet and roast for 25–30 minutes, flipping halfway, until caramelized and slightly crispy.
Meanwhile, combine pearl couscous and vegetable broth in a saucepan. Bring to a boil, then reduce heat, cover, and simmer for 10–12 minutes, or until the liquid is absorbed. Fluff with a fork and stir in olive oil and lemon zest. Set aside to cool slightly.
In a small bowl, whisk together tahini, lemon juice, olive oil, garlic, cumin, salt, and pepper. Slowly add 2 to 4 tablespoons of water, whisking until smooth and creamy. Adjust consistency and seasoning to taste.
In a large serving bowl, combine the cooked couscous, pomegranate seeds, pistachios, parsley, mint, and red onion. Add the roasted carrots and chickpeas, then drizzle with the tahini dressing. Toss gently to coat.
Garnish with extra herbs and a drizzle of olive oil if desired. Serve warm or at room temperature.