Veal is the meat of young cattle (calves), in contrast to the beef from older cattle. Though veal can be produced from a calf of either sex and any breed, most veal comes from male calves (bull calves) of dairy cattle breeds. Generally, veal is more expensive than beef from older cattle.1
Bread and fry the cutlets: Combine breadcrumbs, pecorino Romano, 1/2 teaspoon salt, and some pepper. Put flour, eggs, and breadcrumb mixture in 3 separate dishes. Dredge cutlets in flour, shaking off excess. Dip in egg, letting excess drip off. Dredge in breadcrumbs to coat. Let stand for 30 minutes.
Heat oil in large straight-sided skillet over medium-high heat. (Oil is ready when a breadcrumb sizzles when dropped in.) Working in batches, fry cutlets until golden, 3 to 4 minutes per side. Transfer to a paper-towel-lined baking sheet. (If oil gets too dirty, discard, and heat an additional 1/4 cup.)
Assemble the dish: Preheat oven to 375 degrees. Spread 3/4 cup marinara sauce in the bottom of a 9-by-13-inch baking dish. Arrange a single layer of cutlets on top. Top with 1 cup sauce, covering each piece. Sprinkle with mozzarella and pecorino Romano. Cover with foil. Bake until bubbling, about 10 minutes. Uncover; bake until cheese melts, about 2 minutes more.