Roll out thawed pastry sheet on counter (over sprinkled flour, if sticking). Spread the Aloue.tte cheese on pastry sheet - leaving a 1/2" border. Arrange spinach and then prosciutto slices over cheese spread.
Starting at one end, roll up pastry sheet jelly-roll style, keeping the roll as tight as possible. Wrap in plastic.
Refrigerate until firm (2-3 hours minimum and up to 2 days) or freeze for future use.
When ready to bake, thaw in fridge for several hours, remove from fridge, cut into thin 1/4"-1/2" slices with a sharp, serrated knife.
Spray cookie sheet with cooking spray or line with parchment paper. Lay each slice onto cookie sheet 1" apart. Brush with egg to coat each piece.
Bake 10-12 minutes until golden brown. Serve warm.