Pour Kosher salt into a 9" x 13" baking pan. Rinse the potatoes and set them into the salt, giving them a push to submerge them a bit. Cut up the head of garlic and place several cloves (to taste) around the pan. Next, place several sprigs of rosemary in the pan as well. Cover tightly with foil.
Preheat your Yoder Smokers YS640 (or other grill) to 450°F. Place the pan onto the grill and let them cook 1 hour 20 minutes.
Pull the potatoes from the grill and set it to 500°F. Remove the garlic and rosemary from the pan and baste the tops of the potatoes with olive oil. Place the potatoes back on the cooker to finish for roughly 20 more minutes. While the potatoes are finishing, mince the garlic and rosemary. Combine these with the softened unsalted butter and Cattleman's Grill Tri-Tip Seasoning.
Once the potatoes are tender when pierced with a fork, remove them. Let them rest to cool for five minutes. Serve topped with the garlic and rosemary butter. Enjoy!
**Adapted from America's Test Kitchen and proven in the All Things Barbecue Test Kitchen