Fill large pot with cold water. Add baby potatoes and 1 tsp salt using measuring spoon. Bring to boil over high heat with lid off. Boil 15 minutes till fork pierces easy but firm. Drain in colander.
Preheat oven to 450°F. Line baking sheet with parchment. Place potatoes on sheet. Smash each to ½-inch thick using potato masher-aim for rough edges. Drizzle olive oil over tops with measuring spoon.
Sprinkle garlic powder, rosemary, salt, and pepper evenly using measuring spoons. Rub in gently with fingers for full coat. Roast middle rack 20 minutes till edges golden crispy.
Broil 2-3 minutes for extra crunch-watch close no burn. Pull sheet, sprinkle parsley with spoon. Serve hot piled on plate.