I've tried many kinds of pot roasts in the slow cooker and the oven and this one was the most delicious one I've ever made! I used a 3 pound roast so I did a little math to adjust the times appropriately.
1 (5 pound) standing beef rib roast (I used a regular roast and it turned out great!)
2 teaspoons salt
1 teaspoon ground black pepper
1 teaspoon garlic powder
Allow roast to stand at room temperature for at least 1 hour.
Preheat the oven to 375 degrees F (190 degrees C). Combine the salt, pepper and garlic powder in a small cup. Place the roast on a rack in a roasting pan so that the fatty side is up and the rib side is on the bottom. Rub the seasoning onto the roast.
Roast for 1 hour in the preheated oven. Turn the oven off and leave the roast inside. Do not open the door. Leave it in there for 3 hours. 30 to 40 minutes before serving, turn the oven back on at 375 degrees F (190 degrees C) to reheat the roast. The internal temperature should be at least 145 degrees F (62 degrees C). Remove from the oven and let rest for 10 minutes before carving into servings.