Preheat the grill on medium low...roughly 325 degrees F.
After the potatoes have been scrubbed and rinsed, cut the in half lengthwise. Now cut each half into 3 wedges lengthwise. Place wedges on a rimmed baking sheet and brush all sides with olive oil. Sprinkle all sides with salt, pepper and rosemary.
Place the sweet potatoes on the grill and cover, turning every 8-10 minutes, until tender and brown, approximately 15-25 minutes. Remove from the grill and place on a platter.
Drizzle with a little more oil just before serving.