In a small bowl, mix kosher salt, black pepper, garlic powder, ground sage, and dried thyme with a fork.
Rub the seasoning mixture evenly over the entire ribeye roast, pressing to adhere.
Place the roast fat side up on a rack in a roasting pan and let it sit at room temperature for about 1 hour.
Preheat the oven to 500°F.
Insert an oven-safe meat thermometer into the center of the roast, set to alert at 135°F for medium-rare.
Roast the meat at 500°F for 15 minutes.
Reduce oven temperature to 350°F and continue roasting until the thermometer reaches 135°F, approximately 1 hour more.
Remove the roast from the oven without removing the thermometer and loosely cover with foil.
Rest the roast for 20 minutes to allow juices to redistribute.
Cut the roast against the grain into four ½-inch slices and serve.