Pat prime rib dry with paper towel and generously season all sides with salt. Cover and refrigerate for 4 hours to overnight.
When ready to cook, remove prime rib from fridge and let stand at room temperature for 1 hour. Pat dry with paper towel.
Preheat Traeger or oven to 250F.
In a bowl, combine the butter, parsley, rosemary, thyme and sage. Mix until incorporated.
Evenly spread the mixture on all sides of the rib roast. Generously season all sides with black pepper and place the roast on a wire rack set over a rimmed baking sheet.
Transfer to the Traeger or bottom rack of your oven and cook until the internal temperature reaches 120F (assuming you like your meat medium-rare), approximately 2 hours for a 5 pound roast. If using a Traeger, insert the meat probe into the thickest part of the roast for an accurate temperature reading.
Preheat a cast-iron skillet over high heat. Add the rib roast along with 2 tablespoons of the rendered butter reserved in the baking sheet. Cook 60 seconds, using a large spoon to continuously baste the roast as it sears in the skillet. Flip and cook an additional 60 seconds, continuing to baste. Repeat on all sides until a crust develops on the outside of the meat and the internal temperature of the roast reaches 135F.
Transfer to a carving board and let it rest 10 minutes before carving.