Preheat oven to 450 degrees F. Brush roast with mustard, and then sprinkle with salt, pepper and rosemary. Roast 20 minutes, then reduce heat to 325 degrees F, and continue cooking to desired doneness. (Allow 20 minutes per pound for rare, 25 for medium-rare and 30 for medium). Remove from oven and rest 15 minutes before slicing thinly. Serve with the following side dishes if desired.
Combine 1 cup of mayonnaise with 1/2 cup horseradish (or to taste), a splash of Worcestershire and 2 Tbsp. finely chopped green onions or parsley.
Asparagus with Lemon Dijon Vinaigrette
Trim 1 1/2 pounds of asparagus. Cook in boiling water until just tender, and then drain, cool in ice water, drain again and pat dry. (Treat asparagus kindly through all of these steps). Arrange on a serving platter and top with a dressing made by mixing together a 1/2 cup olive oil and 2 tsp. Dijon mustard with lemon juice, honey, salt and pepper to taste. Garnish top with finely chopped red pepper.