In a large Dutch oven or heavy 6-quart saucepan over medium heat, heat 1/4 cup of the olive oil. Season the meat with 2 teaspoons salt. Place the beef in the pan in one layer as much as possible and let brown, undisturbed, for 10 to 14 minutes (it’s okay if the tops still look raw).
Meanwhile, preheat the oven to 400°F. Remove the leaves from the remaining rosemary sprig. Put the potatoes in a large baking dish with the remaining 2 tablespoons olive oil, 1/2 teaspoon salt, 1/4 teaspoon pepper, and the rosemary leaves and toss to coat. Roast the potatoes, gently turning with a spatula once or twice during cooking, until browned, 40 to 50 minutes.