Preheat the oven to 350 degrees F (175 degrees C).
Heat oil in a skillet over medium heat. When hot, add onion, mushrooms and garlic. Cook and stir until tender, about 5 minutes. Set aside to cool slightly.
On a lightly floured surface, roll out the pizza crust dough to a 12x9 inch rectangle. Cover with layers of vegetables, cheese and roast beef slices to within 1/2 inch of the edges. Starting at the longest side of the dough, roll across to the other side and pinch seam to seal.
Place seam side down on a greased baking sheet.
Whisk together the egg white and water with a fork and brush on top of the roll.
Sprinkle Italian seasoning over the top of the roll.
Bake for 25 minutes in the preheated oven, or until golden brown.