Stir the garlic and rosemary sprigs through the tomatoes. Spread them out in a roasting tin and cook in a preheated oven, 200°C (400°F), Gas Mark 6, for 30 minutes.
Meanwhile, lightly spray a casserole dish with oil and gently cook the onion for 10 minutes. Add the chopped rosemary, chilli, stock and chickpeas, season to taste, cover and transfer to the oven for 20 minutes or the remainder of the tomato cooking time.
When the tomatoes are cooked, stir them into the chickpeas with all the juices from the roasting tin. Check the seasoning and, if liked, serve with baked potatoes and a green salad.