01 - Preheat the air fryer to 350°F for 3 minutes to ensure proper crisping.
02 - Unroll the refrigerated croissant dough and separate into 4 individual triangles.
03 - Spread a thin layer of Dijon mustard onto each triangle if using, distributing evenly across the surface.
04 - Place 1 slice of roast beef, 1 slice of ham, and 1 slice of cheese on the wide end of each dough triangle.
05 - Roll each croissant starting from the wide end toward the point, tucking in the sides to securely enclose the filling.
06 - Place croissants seam-side down in the air fryer basket, leaving space between each to allow air circulation.
07 - Brush tops lightly with softened butter if desired. Air fry for 7 to 8 minutes until golden brown and crispy.
08 - Let croissants cool in the basket for 2 to 3 minutes before serving to allow filling to set.