Preheat the oven to 220c, 200C for a fan-assisted oven, 425F or Gas 7.
In a bowl, mix the chickpeas, olive oil, and spices, except the sumac. Lay on a baking g tray lined with parchment paper and roast for 18-20 minutes until crispy and golden. Set aside to cool.
To make the dressing, mix all the ingredients together in a bowl and season to taste. Add a splash of water if the dressing is still too thick.
When the chickpeas are cool, toss them with the sumac. Mix the diced salad ingredients with the roasted chickpeas and spoon over a generous amount of dressing.
Transfer to a serving bowl and serve topped with parsley