In the bowl of a food processor, place the mushrooms, spinach, egg whites, 1/4 cup Parmesan, pepper, garlic, salt, Italian seasoning, and Worcestershire sauce. Pulse until well blended.
Transfer the mushroom mixture to a large mixing bowl. Add the ground turkey. Using your hands, combine the whole mixture, being careful not to over-mix. Form turkey mixture into 8 equal-size meatballs.
Heat a nonstick 12-inch pan over medium heat and add olive oil. Add the meatballs and brown on all sides, about 10 minutes total. Drain any liquid in the pan and discard. Return meatballs to heat and add crushed tomatoes. Bring to a simmer, then cover and cook meatballs for 15 minutes, stirring occasionally.
Split rolls in half lengthwise and remove bread from center of each side of the roll, being careful not to puncture the crust. Fill each half of the roll with 2 meatballs and 1/4 of the sauce. Place each half roll on a nonstick cookie sheet and sprinkle with the remaining 1/4 cup Parmesan. Place rolls under the broiler for about 1 minute or until cheese starts to melt. Serve immediately.
Recipe courtesy of Juan-Carlos Cruz