Roast beef is a dish of beef which is roasted in an oven. Essentially prepared as a main meal, the leftovers are often used in sandwiches and sometimes are used to make hash. In the United Kingdom, United States, Canada, Ireland, New Zealand and Australia, roast beef is one of the meats traditionally served at Sunday dinner, although it is also often served as a cold cut in delicatessen stores, usually in sandwiches. A traditional side dish to roast beef is Yorkshire pudding.
Roast beef is a signature national dish of England and holds cultural meaning for the English dating back to the 1731 ballad "The Roast Beef of Old England". The dish is so synonymous with England and its cooking methods from the 18th century that the French nickname for the English is "les Rosbifs".
The beef on weck sandwich is a tradition in western New York dating back to the early 1800s. Roast beef is sometimes served with horseradish or horseradish sauce. In Denmark it is mostly used in open sandwiches, called smørrebrød.
The roast beef sandwich commonly comprises bread, cold roast beef (either the leftovers from a homemade dinner or deli meat), lettuce, tomatoes, and mustard, although it would not be uncommon to find cheese, horseradish, fresh/powdered chili pepper and red onion.