To make popovers, preheat oven to 450 degrees F. Beat eggs, and then mix in milk and water. Whisk in flour until just combined. Stir in green onions and rosemary. Season to taste. Pour batter into a well vegetable-sprayed, 12-slot, non-stick muffin tin. Bake 10 minutes. Reduce heat to 325 degrees F and bake 35-40 minutes, or until puffed and golden. When cool enough to handle, carefully remove from tin and reserve.
Place roast bone-side down in a roasting pan. Sprinkle with thyme, pepper and salt. Cook to desired doneness, allowing 20 minutes per pound for rare, 25 for medium rare, and 30 for well done. When beef is ready, transfer to a plate, loosely cover, and rest 10-15 minutes before slicing. Reheat popovers in the oven while beef rest. To make jus to serve with the roast, remove fat from pan, pour in three cups of beef stock, and simmer 5-10 minutes.