Mustard-Crusted Prime Rib Roast

1 (5-pound) boneless prime rib roast

1/2 cup whole grain mustard

6 cloves garlic, minced

Leaves from 3 sprigs fresh rosemary, minced

Vegetable oil

Kosher salt

Freshly ground black pepper

Heat oven to 450F. Let roast sit at room temperature 30 minutes. Season all sides with salt and pepper. 

In a small bowl, stir together mustard, garlic and rosemary. Season lightly with salt and pepper. 

In a large skillet, heat 1/4 cup vegetable oil until hot. Sear roast until browned on all sides, about 3 minutes per side. Set aside until cool enough to handle, then coat the outside with mustard mixture and transfer to a roasting pan. 

Roast at 450F for 20 minutes, then turn the oven down to 350F and continue to cook until internal temperature is 120F, for medium rare. (Roast about 15 minutes/pound, roughly an hour or so.) 

Let roast stand, tented with foil, for 30 minutes. Slice into 1-inch slices and serve.