1. Place oven rack on lowest shelf. If you have a stone, place it on rack. Preheat oven to 550°F, or your oven's highest temperature, for 45 minutes.
2. In a medium bowl, mix ricotta, mozzarella, Parmesan, oil, garlic, rosemary, salt and pepper.
3. Dust a 14-inch-wide pizza peel with cornmeal, then flatten dough on top. Using lightly floured fingers or a floured rolling pin, stretch dough into a 13- to 14-inch round. (Sprinkle peel with more cornmeal if necessary to make sure crust slides around easily on peel.) Spread cheese mixture in an even layer on dough, leaving a 1-inch border.
4. Carefully slide pizza onto stone. Bake until crust is just slightly charred on top and golden on bottom (lift an edge to check) and cheese has melted, about 8 minutes. Transfer pizza to a cutting board and let it rest for a minute or 2 before serving.