Grease a cookie sheet; set aside. Preheat oven to 375 degree F. Unroll crescent roll dough and separate into 8 triangles. Cut each triangle in half lengthwise, forming 16 long, narrow triangles. Place about 1/2 teaspoon of chocolate-hazelnut spread on wide on wide end of each triangle. Brush each banana slice with some of the lemon juice. Place a banana slice on top of spread. Roll dough around bananas. Place bites on prepared cookie sheet.
In a small bowl beat together egg yolk and water. Brush the dough of each bite with the egg yolk mixture. Bake for 11 to 15 minutes or until golden brown. Transfer to a wire rack; cool 10 minutes before serving. Serve within 4 hours. Make 16.