Preheat oven to 450 degrees F. Bring a large sauce pan of water to a boil. Scatter the cornmeal evenly over a baking sheet.
On a lightly floured work surface using a rolling pin to roll out the pizza dough to roughly 12 inches round. Transfer the dough to the prepared baking sheet and set aside.
Once the water has come to a boil, add teh potatoes and parboil for 2 minutes. Use a slotted spoon to transfer them to a kitchen towel or several layers of paper towels to absorb excess water. Repeat this process with the squash.
Coat the pizza dough with the olive oil, then season with salt and pepper. Arrange the potato slices in an overlapping circle along the outside of the dough. Arrange the squash slices over the center of the pizza. Season again with salt and pepper.
Spread the cheese evenly over the pizza, then sprinkle the rosemary. Bake for 15 to 20 minutes, or until cheese is lightly browned.