Position a rack in the lower third of the oven, place an inverted baking sheet on top and preheat to 500 degrees . Using oiled hands, stretch the pizza dough to fit a parchment-lined baking sheet.
In a large skillet, heat 1 tablespoon olive oil over medium heat. Add the sausage and cook, breaking it up, until no longer pink, about 5 minutes. Remove from the pan and pour out any remaining grease. In the same skillet, add 2 tablespoons olive oil, the onion and peppers and cook until softened, about 5 minutes. Season with salt, pepper and the rosemary.
Scatter the sausage, onion and peppers across the pizza dough, leaving a 3/4-inch border. Dollop with the ricotta and sprinkle the parmesan on top; drizzle with the remaining 1 tablespoon olive oil. Set the baking sheet on the inverted baking sheet in the oven and bake until the crust is crisp and golden-brown, about 20 minutes.