01 - Set air fryer to 350°F and preheat for 3 minutes.
02 - Unroll croissant dough and separate into 4 individual triangles.
03 - Spread thin layer of Dijon mustard onto each triangle if desired.
04 - Place 1 slice roast beef, 1 slice ham, and 1 slice cheese on wide end of each triangle.
05 - Roll from wide end toward point, tucking sides to seal filling inside.
06 - Place croissants seam-side down in basket, ensuring they do not touch each other.
07 - Lightly brush tops with softened butter for golden finish.
08 - Cook for 7-8 minutes until golden brown and crisp. Cool 2-3 minutes before serving.