Add all the ingredients, except for the 4 sliced tomatoes, in a baking pan (about 25x35 cm) and mix well. Spread them all over the baking pan and top up the sliced tomatoes to cover them as much as possible. Brush them with some olive oil. Bake in a preheated oven at 180°C/356°F for about 2 hours.
You can make many variations by replacing with your favorite vegetables, herbs or spices.
Depending on your oven, it may take more or less time. So, when it seems almost ready, try it out and decide accordingly.