Thaw prime rib in refrigerator for 48 hours.
In a small bowl, whisk dry seasonings together.
Remove from refrigerator, pat dry on all sides with paper towel, rub with 1/3 cup grapeseed oil, and season generously all over with dry seasonings.
Allow roast to come to room temperature over about 30 minutes.
Preheat oven to 250 degrees Fahrenheit.
In a large cast iron-pan, add remaining grapeseed oil and bring to medium-high heat.
Sear roast on all sides until golden brown all over, about 2 to 3 minutes per side.
Place seared prime rib roast on a wire rack-lined sheet pan and place in the preheated oven.
Cook until internal temperature is 10 degrees below desired cooking doneness – about 1 hour 30 minutes for recommended medium-rare doneness. Use Omaha Steaks roast cooking chart to determine cooking time for your preferred doneness.
Allow to rest for 15-20 minutes before slicing.
Serve with jalapeño crema and roasted vegetables.