Preheat the oven to 225°F (107°C). Rub the prime rib roast with olive oil, then season generously with kosher salt, black pepper, garlic powder, and fresh rosemary.

Roast the Prime Rib

Place the seasoned prime rib on a rack in a roasting pan. Slow roast in the preheated oven for approximately 3 to 4 hours, or until the internal temperature reaches 130°F (54°C) for medium-rare.

Rest the Meat

Remove the roast from the oven and tent it with aluminum foil. Let it rest for at least 20-30 minutes before slicing.

Horseradish Cream Preparation

Mix the Horseradish Cream

In a bowl, combine the prepared horseradish, sour cream, Dijon mustard, lemon juice, and salt. Mix well until smooth and creamy. Adjust seasoning to taste.

Jus Gras Preparation

Prepare the Jus

In a saucepan, combine beef stock and red wine. Bring to a simmer over medium heat and reduce by half. Stir in butter, fresh thyme, and season with salt and pepper to taste.