Put potatoes in a large pot and cover with water by at least 3 inches. Add salt and bring to a boil over high heat. Reduce heat and simmer potatoes until fork tender, about 25 minutes.
Drain potatoes and return to pot to cool slightly. Roughly smash potatoes in pot with a masher or a large fork.
Heat a large nonstick skillet over high heat. Add the bacon and cook until bacon is crispy and has given up most of its fat. Lower the heat to medium-high, add the rosemary and season with salt and pepper. Make sure bacon and rosemary are evenly distributed in the pan then add the potatoes.
Pat down with a spatula so the potatoes are in an even layer. Season the top of the potatoes with salt and pepper.
Cook until a nice brown crust has formed on the bottom, about 5 to 7 minutes. Use the spatula to flip the potatoes, cook until brown on the other side, about 5 minutes.