1 hour before cooking, pull Rib Roast out of the refrigerator and let it sit at room temperature.
Preheat the oven to 325F and make sure your oven rack is in the center of the oven. Generously cover the roast on all sides with salt and pepper. Place a wire rack inside of a baking dish or roasting pan.
Heat a large skillet, preferably cast iron, over high heat and add olive oil to pan. Carefully, sear the roast on all sides, except cut sides, until a nice brown crust forms, approximately 7-9 minutes. For this, I recommend using 2 sets of tongs and to flip, grab the cut sides on the roast with your tongs.
Place the roast on the wire rack set in the baking sheet or roasting pan bone side down. Rub the Butter all over the exterior of the roast, then evenly distribute the smashed Garlic, followed by 10 sprigs of Rosemary and Thyme (tuck it in all of the crevasses!). Place 3 unpeeled Garlic Cloves on the wire rack by themselves (these are for the Horseradish cream sauce).
Place the roast into the oven and set the timer for 40 minutes. After 40 minutes, carefully remove the 3 unpeeled garlic cloves from the oven and set the time for another 1 hour and 20 minutes.
While the roast continues to cook, make your Horseradish Cream Sauce. Peel the skin from your Garlic- the Garlic should resemble a paste at this point and add the Garlic to the food processor with the remaining Rosemary (leaves only, removed from sprig), Sour Cream, Horseradish, Lemon juice and Salt and Pepper, to taste. Blend until smooth, adjust seasoning, as needed. Cover and place in the fridge until ready to use.
After the roast has cooked for the first 2 hours, pull it out of the oven and check the temperature. Insert a thermometer into the center of the roast.
-Rare: you're looking for a temperature between 120F- 125F (it should be done after the 2 hour mark).
-Medium rare: you'll want a temperature between 130F- 135F (cook time should be about 2 hours and 15 minutes)
-Medium: 140F- 145F (2 hours and 30 minutes of cook time)
When your roast has reached your desired temperature, pull it out of the oven, tent it with foil and let it rest for 10 minutes. Discard Herbs and Garlic from Roast and Remove twine- meat should easily separate from the bone. Then carve and serve with Horseradish Cream Sauce.
*Pro tip: arrange additional Herbs and Garlic Cloves on platter on roast for added aesthetics- your guests will ooohhh and aaahhh!