01 - Preheat the air fryer to 350°F for 3 minutes.
02 - Unroll the croissant dough and separate into 4 triangles.
03 - If desired, spread a thin layer of Dijon mustard onto each triangle.
04 - Layer 1 slice of roast beef, 1 slice of ham, and 1 slice of cheese onto the wide end of each triangle.
05 - Roll up each croissant, starting from the wide end and tucking in the sides to seal the filling.
06 - Place croissants seam-side down in the air fryer basket, ensuring they don't touch.
07 - Brush lightly with softened butter if desired.
08 - Air fry for 7-8 minutes, or until golden and crisp. Let cool for 2-3 minutes before serving.