Preheat oven to 350 degrees. Begin chopping spinach and put it in a large mixing bowl. Add feta, mozzarella, red pepper flakes, salt and pepper. Toss thoroughly and set bowl aside. Unroll crescent dough and divide into triangles. Using a spoon, place tiny heaps of spinach mixture on the wide part of the triangle. Roll them up. Place on a greased cookie sheet. Before putting them in the oven lightly brush each roll with the egg white. Bake for 15 minutes or until golden brown.