Preheat oven to 375F. Lightly spray a baking sheet with cooking spray and set aside. Remove sausage from casings and saute in a large frying pan, breaking up with a spoon to brown. Add black pepper and red pepper flakes and cook until sausage is cooked through. Drain the sausage and set aside in a large bowl to cool, about 5 minutes. Add grated mozzarella and eggs to the sausage and stir until well combined. Roll out pizza dough to make a large circle ( about 16 inches in diameter). Place sausage mix in the center and spread to about one inch from the ends. Turn over 1/2 inch of the dough on top, bottom and sides. Roll (not too tight) the bread so that the seam remains on the bottom. In a small bowl, beat 1 egg and baste bread (don’t forget the ends!) with a brush. Gently placed rolled bread on prepared baking sheet. Bake for 50 minutes, turning pan every 20 minutes for even browning. Remove bread from oven and place on rack to cool.