Put the tomatoes in a large bowl and crush them between your fingers. Add the garlic and crushed chillies, then stir in half the oil. Season with salt, cover and leave to infuse.
Heat a baking sheet in a preheated oven, 240°C (475°F), Gas Mark 9. Place 1 pizza dough ball on the base only of a well-floured, 23 cm (9 inch) loose-bottomed tart tin. Push down on the dough with your fingertips, pressing it out to fill the base, leaving the border slightly thicker. If you get any tears, forcefully pinch the dough around the hole back together.
Spoon a quarter of the tomato mixture over the base, then brush the border with oil to glaze. Remove the heated baking sheet from the oven, slide the tin on to it, then quickly return to the oven. Bake for 7–8 minutes until crisp and risen. Scatter with a quarter each of the mozzarella and rocket and serve immediately. As the first pizza cooks, prepare the next for the oven.