Cook the rice according to the directions on the package. Preheat the oven to 180°C (356 F). Cut the tomatoes in half and place them on a baking tray lined with baking paper. Peel and cut the onion into wedges and the garlic bulb in half horizontally. Place with the tomatoes. Drizzle everything with half the oil. Roast the tomatoes, onion and garlic in the middle of the oven for about 30-40 minutes (depending on your oven). In the last 10 minutes spread the Italian herbs over tomatoes and onions.
Meanwhile, heat the rest of the oil in a stockpot and fry the peeled tomatoes over low heat for 2-3 minutes. Remove the baking tray from the oven and let it cool for 5 minutes. Squeeze the roasted garlic from the skin. Add the onion, garlic, roasted tomatoes, water and roasted herb leaves to the peeled tomatoes in the stockpot. Bring to a boil with the lid on the pan. Let it simmer for 15 minutes on low heat. Puree the soup with an immersion blender and season with pepper and garlic powder.
Tear the mozzarella into strips. Ladle the soup into bowls and divide the rice and mozzarella on top. Sprinkle with salt and pepper.
Notes
You can make the soup up to and including step 2 to 2 days in advance. Freezing is also possible (maximum 3 months). Thaw and reheat the soup over medium heat.