Preheat oven to 450 F. Wash potatoes well and cut into 1-inch chunks. Rinse starch off potatoes, then place in a pot.
Cover potatoes with water and add 1 tablespoon salt and bring to a boil. Reduce heat to simmer and cook until potato edges are soft but not cooked all the way through, about 5 minutes.
Transfer potatoes to a heat-safe container with lid, drizzle with olive oil, then sprinkle with rosemary and remaining teaspoon salt. Cover container and shake to roughen edges of potatoes. Spread potatoes in single layer on baking sheet.
Bake 30 to 40 minutes, flipping potatoes every 15 minutes until brown and crispy. Serve immediately.