Preheat a grill to medium-high (~400F) or start a campfire so you will have embers to work with.
Half or quarter the potatoes so they are about 1"x1". Add them to a bowl with the chopped rosemary, garlic powder, salt, and oil. Toss to coat the potatoes.
Roll out a large sheet of foil, followed by a slightly smaller sheet of parchment paper. Transfer the potatoes to the potatoes to the parchment, keeping everything in an even layer.
Cover the potatoes with another sheet of parchment and foil, then crimp the edges together to seal and create a packet.
Place over on your campfire grill grate over medium heat. If you’re using a propane grill, you can lower the top. Cook on each side for 12 minutes, for 24 minutes total.
Remove from the heat, allow to cool slightly, and open up the foil. You can top with additional rosemary and use any remaining sprigs for garnish. Enjoy!