Preheat oven to 325 degrees. Combine garlic, salt, pepper, oil and sage. With the netted Prime Rib Roast fat side up, rub spice mixture evenly over it and place it in a shallow roasting pan. Place the tomatoes evenly around the roast and drizzle with olive oil. Season tomatoes with the remaining seasoning mixture. Insert meat thermometer into thickest portion of meat center. Place meat fat side up on rack in a shallow roasting pan. Roast in oven until meat thermometer registers 135 degrees (approximately 1 to 1 ½ hours) for medium rare or 145 degrees (approximately 1 ½ to 2 hours) for medium. Cover with foil tent and allow to stand 15-20 minutes. Remove netting. While roast is resting, place all tomatoes and juices from roasting pan in a medium pot and bring to a boil. Reduce heat to a slow simmer for 10 to 15 minutes to allow the tomatoes to break up further. Spoon the tomato jus over the slice roast.