Arrange oven racks in the center of the oven set 6 inches apart. Place a pizza stone on each oven rack and preheat oven to 500˚F.
Hand stretch 1 dough ball into a 12x12-inch square.
Place 2 cups of mozzarella onto center of dough and spread evenly leaving 3 inches of dough on each side uncovered. Evenly distribute roast beef onto mozzarella to cover. Spread giardiniera onto roast beef. Sprinkle with 1 tablespoon of Parmesan.
Using a pizza cutter, create seven 2-inch cuts approximately 1-inch apart down each side flap of the dough.
Starting from the top, pull one strip of dough across the toppings towards opposite flap of dough. From the top of opposite flap just pulled, pull top strip of dough towards opposite flap, overlapping previous strip. Continue to alternate, stretching and overlapping each piece of dough until you arrive at the bottom.
Once you get to the final piece of dough, wrap the strip around the bottom to create a point, tucking the strip under the Stromboli to hold it in place. Gently lift Stromboli and place onto a half sheet pan lined with parchment paper. Cover with plastic wrap.
Repeat this process with remaining 2 dough balls (if making all 3). Once the stromboli are on the sheet pan, brush with egg wash. Sprinkle with sesame seeds (optional).
Bake for 22-25 minutes or until Stromboli are golden brown. Allow to cool for 5 minutes before serving.