Preheat your oven to 400°F (200°C).
Roll out the pizza dough on a floured surface into a rectangle.
Spread marinara sauce evenly over the dough, leaving a border.
Sprinkle mozzarella cheese across the sauce.
Layer pepperoni, sausage, bell peppers, and olives on top of the cheese.
Sprinkle Italian seasoning over the fillings.
Roll the dough tightly from one long end to the other, sealing the edges.
Place the rolled stromboli seam-side down on a baking sheet.
Beat the egg and brush it over the top of the stromboli for a glossy finish.
Bake for 25-30 minutes until golden brown; allow to cool before slicing.