Preheat your oven to 400°F (200°C).
Line a baking sheet with parchment paper to prevent sticking.
On a lightly floured surface, roll out the pizza dough into a rectangle about ¼ inch thick.
Spread the marinara sauce evenly over the dough, leaving a 1-inch border around the edges.
Layer the pepperoni, salami, and ham evenly over the sauce.
Sprinkle the mozzarella and Parmesan cheese over the meats, followed by the sliced bell pepper and onion.
Season with Italian seasoning, salt, and pepper to taste.
Starting from one long end, carefully roll the dough away from you, creating a tight log. Pinch the seams and ends to seal.
Place the Stromboli seam-side down on the prepared baking sheet.
Brush the top with beaten egg and drizzle with a little olive oil.
Bake in the preheated oven for 25 minutes or until golden brown.
Allow to cool for a few minutes before slicing.
Serve warm with marinara sauce for dipping.