In a small mixing bowl, combine the 8 tablespoons of softened butter, mixed herbs, and black pepper and beat until fluffy with a wooden spoon. (You can make the herbed butter several days ahead: Cover and refrigerate, but bring to room temperature before using).
Remove any giblets from the turkey cavity and save them for gravy making, if desired. Wash the turkey, inside and out, under cold running water. Dry with paper towels. Place the turkey on a roasting rack in a roasting pan. Tuck the wings behind the back, and tie the legs together with butcher's string.
Using your fingers or the handle of a wooden spoon, gently push some of the herbed butter underneath the turkey skin onto the breast halves, being careful not to tear the skin. Massage the skin to evenly distribute the herbed butter.
Rub the outside of the turkey with the melted butter and sprinkle with the Traeger Pork and Poultry Rub. Pour the chicken broth in the bottom of the roasting pan.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 325F and preheat, lid closed, for 10 to 15 minutes.
Put the roasting pan with the turkey directly on the grill grate. Roast the turkey for 3 hours. Insert the probe from the meat thermometer in the thickest part of the thigh, but not touching bone: You're looking for a temperature of 165F. The turkey should also be beautifully browned with crisp skin. If the temperature is less than that, or if your turkey is not browned to your liking, let it roast for another 30 minutes, then check the temperature again. Repeat until the turkey is fully cooked.
When the turkey is done, carefully transfer it to a cutting board and let it rest for 20 to 30 minutes. Do not tent it with aluminum foil or the skin will lose its crispness. Use the drippings that have accumulated in the bottom of the roasting pan to make gravy, if desired. Carve the turkey and serve.