Take pizza dough out and let it come to room temperature. Preheat oven to 400 degrees. Wipe a 9x13 pan or sheet pan with oil and set aside.
In a skillet, heat the oil over medium heat. Add spinach, mushrooms, onion, salt and pepper. Cook until mushrooms and onion have softened. Remove from heat.
Place the pizza dough into the oiled pan and stretch it to fit the pan, flattening it out until it's a large rectangle.
Spread the ricotta cheese onto the pizza dough, leaving a 1-1 1/2 inch border around the edge of the dough.
Then spoon the spinach and mushroom mixture on top and finish with the garlic powder and a sprinkle of mozzarella cheese.
Carefully roll up the pizza dough and fold the ends underneath.
Mix beaten egg and water in a small bowl. Brush the egg wash on top of the stromboli and sprinkle with Italian seasoning.
Place the stromboli in the oven and cook for 35-40 minutes, or until golden brown and crispy.
Remove stromboli from oven and cool for a few minutes before slicing. Serve with warm marinara sauce for dipping.