At least 1 hour prior to grilling, up to a day before, season and salt your prime rib roast, patting the seasonings into the meat so that it adheres. Allow it to come to room temperature prior to grilling. 

Use butcher's twine to truss the roast to make sure the meat is secured and compact. 

Skewer the roast on your rotisserie spit, so that roast is skewered through the middle, then attach your rotisserie forks and slide into the meat, and tighten the lock screws to secure. 

Fit the ends of the spit into the rotisserie sockets. Place a grill safe aluminum pan below the meat to catch drippings. Turn on your rotisserie so that it begins spinning, then turn your infrared heat  to medium high, if using. Use this to sear the outside of the prime rib for for about 20 minutes, until there is a bit of a crust forming. 

Turn infrared heat off, and use indirect heat to bring the grill to 300 degrees F with cover closed. I turn on my far left and far right burner to medium-low heat to hold at 300 degrees F. If you do not have an infrared rotisserie burner, this is where you’ll start, heating the grill to 300 degrees F. 

Spit roast the prime rib at 300 degrees F, until the internal temperature of the center reaches 120 degrees F. Pause the rotisserie and use an instant-read meat thermometer every 15 minutes to keep tabs on the temp. Thermometer should be inserted into the very center of the prime rib to test for doneness.

When meat has reached 120 degrees F, turn off indirect heat (if using infrared rotisserie burner). Turn infrared rotisserie burner back on medium high to finish searing the outside for a few minutes, until crusty and brown. Internal temperature of center of prime rib should now be at 125 degrees F. If not using the infrared burner, just cook to 125 degrees F. 

Remove spit from grill, and set roast onto a cutting board. Carefully remove prime rib from spit and let meat rest for 15 minutes. Then carve in thin slices and serve warm.