Peel and mash the garlic. Sprinkle garlic with the salt and chop to a fine paste. Mix well in a small bowl with the paprika, cayenne, cumin and oregano. Nick the rib roast in 8 places or so to allow the marinade to penetrate. Spread the marinade over the roast, cover, and marinate for 48 hours. When ready to prepare burritos, grill the roast until just past pink. Slice thinly.