Preheat oven to 450 degrees F; reduce oven temperature to 425 degrees F. In a 10-inch skillet cook bacon over medium heat just until it begins to brown. Drain on paper towels, reserving 1 tsp. drippings in skillet.
Add potatoes and onion to reserved drippings; sprinkle with rosemary, 1/4 tsp. of the salt, and 1/4 tsp. of the pepper. Cook over medium-high heat 5 to 6 minutes or until potatoes are light brown and onion is tender, turning occasionally.
Place pizza crust on a baking sheet;* brush with the 1 tsp. oil. Top with potato mixture and bacon. Bake 10 minutes or until edge of crust is brown.
Meanwhile, for salad, remove 1 tsp. zest and squeeze 1 Tbsp. juice from lemon. In a medium bowl whisk together lemon zest and juice, 3 Tbsp. oil, mustard, and remaining 1/4 tsp. salt and pepper. Add arugula; toss to coat. Pile salad on top of pizza and sprinkle with cheese.
For a crisper crust, bake the pizza directly on the oven rack.