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. Let Cool Slightly, Then Slice And Serve.