Remove the prime rib from the refrigerator at least 2 hours before cooking to allow it to come to room temperature. Preheat the oven to 450°F (232°C).

Pat the roast dry with paper towels to remove excess moisture.

In a small bowl, combine softened butter, minced garlic, chopped sage, rosemary, salt, black pepper, onion powder, and paprika to create the garlic and sage butter.

Loosen the fat cap on the top of the roast with a small knife. Spread half of the butter mixture underneath the fat layer and the remainder over the outside of the roast. Drizzle olive oil over the surface.

Place the roast on a rack in a roasting pan, fat side up, and insert an oven-safe meat thermometer into the thickest part of the roast.

Roast at 450°F (232°C) for 20 minutes to sear the exterior, then reduce the temperature to 325°F (163°C) and continue roasting until the internal temperature reaches desired doneness: 120–125°F (49–52°C) for rare, 130–135°F (54–57°C) for medium-rare, or 140–145°F (60–63°C) for medium.

Remove the roast from the oven and tent loosely with foil. Let it rest for 20–30 minutes.

Carve the roast against the grain into ½-inch thick slices and serve, garnished with fresh rosemary and sage if desired.