<human>:  How do I make a roast beef sandwich?
<bot>: To make a roast beef sandwich, start by gathering the necessary ingredients: sliced roast beef, bread, lettuce, tomato, and mayonnaise. Spread an even layer of mayonnaise on each slice of bread, then layer the roast beef, lettuce, and tomato on one side. Top with the other piece of bread, then cut the sandwich in half. Enjoy!