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.
In a medium bowl, mix ricotta, mozzarella, Parmesan, oil, garlic, rosemary, salt and pepper.
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.
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.