Preheat the oven to 325 degrees Fahrenheit.
Combine onion and garlic powders with thyme in a small bowl.
Rub over the whole roast.
Place the roast with the fat side in a large roasting pan.
Insert the thermometer into the middle of the roast.
Roast to a temperature of 120 degrees for about 2 1/2 to 3 hours.
Meanwhile, mix carrots, parsley flakes, salt, and pepper.
Spoon on the roast’s fatty side.
Reheat the beef in the oven.
Roast until a meat thermometer reads 130 degrees for rare, or 140 degrees for medium, approximately 30 minutes and 1 hour, respectively.
Place the meat on the chopping board.
Let stand for 20 minutes. Meanwhile, preheat the oven to 400 degrees for the Yorkshire pudding puffs.
Remove drippings from the roasting pan and discard the fat.
For Yorkshire pudding puffs, use six tablespoons of drippings.