Preheat oven to 400°F.
Lightly flour a surface and roll out the pizza dough into a large rectangle, about 13x9 inches. Optionally, place the dough on parchment paper at this stage to allow for easier transfer later.
Starting with pepperoni, layer the meats and cheeses evenly over the dough, leaving a 1-inch border around the edges.
Sprinkle garlic powder and Italian seasoning evenly over the fillings.
Starting from one of the long edges, carefully roll the dough into a log, pinch the seams to seal and tuck in any overlap.
Transfer the Stromboli to a baking sheet lined with parchment paper, seam side down.
Brush the top with beaten egg and sprinkle with grated parmesan cheese.
Bake in the preheated oven for 25 minutes, or until the crust is golden brown.
Allow the Stromboli to rest for 10 minutes before slicing.
Serve warm with marinara sauce for dipping.