How to Make It
Place dough balls on a baking sheet; cover with plastic wrap. Let rest at room temperature for at least 45 minutes and up to 2 hours. (This will make it easier to stretch.)
Preheat oven to 500°F with rack in lowest position. Lightly flour a work surface. Place 1 dough ball on surface (leave second ball covered); turn to coat in flour. Press firmly with fingertips to flatten. Roll to a 14-by-11-inch oval with a rolling pin. Transfer to a baking sheet.
Top dough with half the pecorino Romano, leaving a ½-inch border around edge. Arrange half the potatoes, slightly overlapping, on top of cheese. Top with 1 tablespoon rosemary and ¼ teaspoon salt. Drizzle with 1 tablespoon oil.
Bake until edge and bottom of crust are golden brown (use a spatula to peek underneath), 10 to 12 minutes. Remove from oven. Dollop with 1 cup ricotta; drizzle with oil and top with several grinds of pepper.
Repeat with remaining dough and toppings.