01 -
Combine mayonnaise, stone ground mustard, and prepared horseradish in a small bowl until smooth.
02 -
Optionally line the air fryer basket with aluminum foil. Place two bottom buns and two top buns in the basket and spread the prepared sauce evenly on each bun.
03 -
Place one slice of Swiss cheese on each bun. Add approximately five slices of roast beef to each bottom bun.
04 -
Cook sandwiches on the air fryer setting at 370°F for 4–6 minutes, until the cheese is melted, meat is warmed through, and buns are lightly toasted. Remove top buns if they brown too quickly and finish cooking.
05 -
Repeat assembly and cooking process for the remaining two sandwiches. Serve immediately with any leftover sauce.