Make cross-cuts through the fat pad on top of the roast, only cutting through the fat – not the meat. Rub about 2 Tbsp. of kosher salt all over the roast. Refrigerate at least 24 hours and up to 4 days.
Preheat oven to 200 degrees. Heat 2 tsp of vegetable oil in a 12-inch heavy skillet until just smoking. Brown the roast on all sides, 6-8 minutes total. Let rest for 10 minutes.
Place the roast on a V-rack or wire rack inside of a roasting or rimmed pan. Season with salt and pepper, and place the oven on a middle rack. Roast until meat reaches 110 degrees (about 3-4 hours).
Turn off the oven, leaving the roast inside, until meat reaches 125 (for medium-rare). This will take between about 60 minutes.
Let rest for 15 minutes, then slice into 1" to 1½" thick slices, like a steak and serve.
Notes
Bone-in Roasts: Use the bones to create your own v-rack for roasting. With a sharp knife, carefully remove cut bones from the roast. Once removed, invert the bones beneath the roast. Use cooking twine to anchor them to the prime rib by tying them on. When inverted, the bones will elevate the roast from the roasting pan, but still provide flavoring and release marrow into the au jus.Leftovers will keep well for up to 4 days in the refrigerator, or 3 months in the freezer. Let the roast beef cool completely before transferring to an airtight container. If freezing, I also suggest you wrap the container in a layer of aluminum foil.