Preheat oven to 200⁰C. Place beef on a rack in a roasting dish.
Combine the butter, garlic, horseradish, mustard and half the marjoram together. Spread butter mixture evenly all over the beef. Sprinkle with remaining marjoram leaves. Season with salt and pepper.
Roast for 45-60 minutes for rare, 60-75 minutes for medium, or 75-90 minutes for well done. For ease and accuracy, use a meat thermometer. Add the vegetables to the tray in the last 20 minutes of baking.
Remove beef, cover it loosely with foil, and rest it in warm place for 10-20 minutes before carving across the grain. Transfer the roasted vegetables to serving plates and top with carved roast. Spoon over some of the pan juices. Serve beef and vegetables with salad.
Try using different coloured baby carrots, such as orange, purple or red.
Dress the salad leaves with a little extra virgin olive oil and some lemon juice.
You can cut the rib roast into steaks and cook on a char-grill if desired and then simply serve with the marjoram, horseradish butter mixture dolloped on top.