Preheat and prep. Heat your oven to 425°F (220°C).
Line a large sheet pan with parchment for easy cleanup. If your pan is small, use two so the vegetables roast instead of steam.
Dry the chickpeas well. Spread rinsed chickpeas on a clean towel and pat dry. This helps them crisp up in the oven.
Season the vegetables. In a large bowl, toss the eggplant, onion, and bell pepper with 2 tablespoons olive oil, cumin, smoked paprika, coriander, red pepper flakes, salt, and a few grinds of black pepper.
Add the chickpeas and toss again. Scatter everything evenly on the sheet pan.
Roast until golden. Place the pan on a middle rack and roast for 25–30 minutes, stirring once halfway. The eggplant should be soft and browned at the edges, and the chickpeas slightly crisp.
Add garlic and lemon. In the last 3–4 minutes of roasting, pull the pan out, drizzle on 1 tablespoon olive oil, sprinkle the minced garlic, and toss.
Return to the oven just until the garlic smells fragrant. Zest the lemon over the pan as soon as it comes out.
Make the tahini drizzle. In a small bowl, whisk tahini with the juice of the lemon and a pinch of salt. It will seize up; add warm water, 1 tablespoon at a time, until it becomes creamy and pourable.
Finish and serve. Sprinkle chopped herbs over the roasted vegetables and chickpeas.
Taste and adjust salt, pepper, or lemon. Spoon onto plates, drizzle with tahini, and add optional toppings like feta or pine nuts. Serve with grains or warm pita if you like.