First prepare the roasted vegetables: prepare the eggplant and zucchini ahead of time by cutting them into 1 inch (2.5 cm) dice, leaving the skins on. Then toss the dice in a level teaspoon of salt and pack them into a colander with a plate on top and a heavy weight on top of the plate. Leave them on one side for an hour so that some of the bitter juices drain out. After that, squeeze out any juices left, and dry the dice thoroughly in a clean cloth. Preheat the oven to gas mark 9, 475°F (240°C).