1. Preheat the oven to 500°. Preheat a pizza stone or oil a large baking sheet.
2. On a floured surface, roll or stretch the dough to an 8-inch round; let stand for 10 minutes. Roll or stretch the dough to a 13-inch round. Transfer to a floured pizza peel or rimless cookie sheet.
3. Heat 1/4 cup of the olive oil in a large nonstick skillet until shimmering. Add all of the diced potatoes and cook over moderately high heat, turning occasionally, until barely tender, about 10 minutes. Add the garlic and rosemary and cook, shaking the skillet, until the garlic is golden and the potatoes are golden brown, about 10 minutes longer.
4. Remove the rosemary sprigs and garlic. Pick off the rosemary leaves and add to the potatoes. Transfer the garlic to a mini-processor. Add the olives and scallion and pulse until finely chopped. Scrape the mixture into the skillet, toss with the potatoes and season with sea salt and crushed red pepper.
5. Transfer half of the potatoes to a bowl and mash coarsely. Spread the mashed potatoes all over the pizza dough, leaving a 1-inch border. Top with the remaining potatoes and brush the crust with 1/2 tablespoon of the olive oil.
6. Slide the pizza onto the hot stone or oiled baking sheet and bake for 10 minutes on the stone or 16 minutes on the sheet. The pizza is done when the crust is golden brown. Transfer to a rack to cool slightly. Drizzle the remaining 2 tablespoons of oil on the pizza and sprinkle with salt. Cut into wedges and serve.
Wine Recommendation: The slightly bitter and briny flavors of the tapenade should be contrasted with a refreshing, low-alcohol Riesling or a fruity red. Two good choices are the 1998 Hugel Alsace Jubilee Riesling and the 1995 Bolla Le Poiane Valpolicella Classico.