Adjust oven rack to upper-middle position and heat oven to 500 degrees.
Toss potatoes with 1 tablespoon oil in large microwave-safe bowl. Cover tightly with plastic wrap and microwave on high power until potatoes are just tender, 3 to 7 minutes.
Meanwhile, combine 2 tablespoons oil, onion, rosemary, goat cheese, and salt and pepper to taste in bowl.
Brush 2 tablespoons oil over rimmed baking sheet.
On lightly floured work surface, roll dough into 16 by 9-inch oval (about ¼ inch thick) and transfer to oiled baking sheet.
Scatter potatoes in single layer over dough and top with onion mixture.
Drizzle with remaining tablespoon oil and season with salt and pepper.
Bake until onions are soft and edges of pizza are well browned, about 15 minutes.
Cut into wedges. Serve.
