Cook the potatoes in boiling water for 10-12 minutes. Drain and let cool enough to handle.
Mix together the oil, garlic, 1 tablespoon of the rosemary, salt red pepper flakes and chili powder.
Transfer the red potatoes to a sealable bag or bowl and pour oil mixture over, tossing to coat. Seal in bag or bowl and let rest for 30 minutes.
Preheat grill or smoker to 425-450°F.
Thread marinated potatoes onto skewers. If using wooden skewers, soak them in cold water for 5 minutes first so they don't burn on the grill. I use metal ones myself (be careful they get hot).
Place the skewered potatoes on a rack in the grill or smoker and cook for around 25 to 30 minutes, turning frequently, until very soft and slightly charred, remove from the grill and serve with remaining rosemary sprinkled on top.