On a lightly floured work surface, roll out the pizza dough to a 12 to 14-inch diameter circle, about 1/4-inch thick. Sprinkle 1/2 of the mozzarella over the dough. Arrange the prosciutto over the cheese in a single layer. Sprinkle with the spinach. Top with the remaining cheese. Take 1 end of the circle and roll the dough up into a thin cylinder, gently folding in the ends. Brush the dough with the olive oil and season with the salt. Place the dough, seam side down, on a parchment lined baking sheet and bake for 25 minutes until the top is golden brown. Allow the pizza to cool for 10 minutes. Using a serrated knife, cut the pizza into 3/4-inch pieces and serve.