Preheat an outdoor grill to medium-high, indirect heat and lightly oil the grate.

Place potatoes into a large pot and cover with water; bring to a boil. Cook over medium-high heat until tender, about 10 minutes. Drain.

Transfer potatoes to a large bowl. Add olive oil, black pepper, garlic powder, rosemary, and salt; mix until potatoes are evenly coated.

Cook potatoes, skin-sides down, on the preheated grill over indirect heat for about 15 minutes, leaving olive oil mixture in the bowl.

Transfer potatoes to a serving plate; drizzle with reserved olive oil mixture.