Spray counter lightly with non-stick cooking spray (or use parchment paper). Roll loaf or combined dinner rolls into a 12x16-inch rectangle. Cover with plastic wrap and let rest for a few minutes. Cook spaghetti according to package instructions. Drain and let cool slightly. Remove wrap from dough. Place spaghetti lengthwise in a 4-inch strip down the center of dough. Tip with sauce and cheese cubes. (I make my spaghetti with italian sausage for added flavor. I also suggest going a bit LIGHT on the sauce, because it will leak out the sides. I speak from experience!) Make cuts 1 inch apart on long sides of dough to within ½-inch of filling. Begin braid by folding top and bottom strips toward filling. Then braid strips left over right, right over left. Finish by pulling last strip over and tucking under braid. Lift braid with both hands and place on large sprayed baking sheet. (or transfer parchment paper to baking sheet). Brush with egg white and sprinkle with Parmesan cheese, parsley and garlic powder, if desired. Bake at 350 for 30-35 minutes or until golden brown. Cool slightly and slice to serve.