1. Place an oven rack on lowest position and preheat to 500°F.
2. On a lightly floured surface, roll dough into a 14-inch round. Generously sprinkle a baking sheet with cornmeal. Place dough on sheet.
3. In a large bowl, stir together garlic and oil. Add potatoes, rosemary and salt. Top dough with potatoes, overlapping, leaving a 1/2-inch border. Sprinkle with Parmesan and pepper.
4. Bake until cheese has melted and crust is crisp, about 13 minutes. Cut into 8 slices. Serve.