Put the oil for the vegetables in a large plastic bag with the garlic, saffron and salt and pepper. Add the vegetables, grip the top edge of the bag to seal and toss together. Set aside for at least 30 minutes.
Make the rouille. Put the tomatoes and red pepper into a small roasting tin. Sprinkle with the garlic, pimenton and salt and pepper, then drizzle the oil over. Roast in a preheated oven, 220°C (425°F), Gas Mark 7, for 15 minutes.
Cool, then peel the skins from the tomatoes and pepper. Purée the flesh in a liquidizer or food processor with any juices from the roasting tin until smooth. Spoon into a serving bowl and set aside.
Tip the saffron vegetables into a large roasting tin and cook in a preheated oven, 220°C (425°F), Gas Mark 7, for 15–20 minutes, turning once until browned. Spoon the vegetables on to individual plates and serve with spoonfuls of the rouille, reheated if necessary.