Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
Roll out the pizza dough on a floured surface into a 10x14-inch rectangle.
Spread marinara sauce evenly over the dough, leaving a 1-inch border.
Sprinkle shredded mozzarella cheese over the sauce.
Add sliced pepperoni and sprinkle with Italian seasoning.
Roll up the dough tightly from the long side, tucking in the ends.
Place the rolled Stromboli seam-side down on the baking sheet.
Brush the top with egg wash and bake for 20-25 minutes or until golden brown.
Melt the butter and mix with garlic powder, then brush over the baked Stromboli.
Let it cool slightly, then slice and serve with extra marinara sauce.