Preheat oven to 350 degrees F. Lightly spray a 13x9" baking pan with non stick cooking spray.
Without separating the individual rolls, carefully slice across the rolls horizontally to create a top layer and bottom layer. Repeat with other pack of rolls. Place bottom layers of both packages of rolls into the prepared baking pan. Depending on the brand of rolls, it might be a tight fit, or you may have to use 2 pans.
Spread a very thin layer of mayonnaise over the bottom layer of rolls, then top with a generous portion of shredded Italian beef. Lay slices of provolone cheese on top of the beef and top with the top layer of rolls.
Combine melted butter and garlic powder and brush over top of rolls. You may have some butter leftover, depending on how liberal you were with brushing it on.
Bake for 7-10 minutes, until rolls are golden brown and cheese is melted.
Sprinkle with minced parsley (optional) and serve.