Preheat oven to 375°F. Season roast with salt and pepper.
In a small bowl, combine garlic, mustard, mayonnaise and horseradish. In another small bowl, combine parsley, thyme, dill and 1 tablespoon of mustard mixture.
Place meat in a roasting pan; coat top with remaining mustard mixture and cook meat until an instant-read thermometer inserted in center of roast registers 120°F.
Coat roast with remaining mustard mixture and press herb mixture onto mustard with your hands.
Continue cooking roast until a thermometer inserted in center of meat registers 160°F for medium, or longer until desired degree of done-ness.
Cover loosely with foil and then let stand 20 to 30 minutes before carving into 12 thick slices.
Notes
Makes 12 serving (12 slices)Serving size is one slice