01 - Preheat the air fryer to 350°F for 3 minutes before beginning preparation.
02 - Unroll the croissant dough and separate into 4 individual triangles on a clean surface.
03 - Spread a thin layer of Dijon mustard onto each triangle if desired for added flavor.
04 - Place 1 slice of roast beef, 1 slice of ham, and 1 slice of cheese onto the wide end of each dough triangle.
05 - Roll each croissant starting from the wide end, tucking in the sides to seal the filling securely inside.
06 - Place croissants seam-side down in the air fryer basket, ensuring they do not touch each other for even cooking.
07 - Lightly brush the tops with softened butter if desired for a golden, glossy finish.
08 - Air fry for 7 to 8 minutes until golden brown and crispy. Let cool for 2 to 3 minutes before serving.