Brush the Sub Roll with olive oil and arrange on a tray.
Combine the turkey meatballs, marinara, and chicken broth in a saucepan and bring to a simmer, approximately 12 – 15 minutes, until hot. (Frozen meatballs will take approximately 20 minutes).
Sprinkle each sub with 2 tsp Parmesan cheese on top of meatballs. Cover the meatballs with 2 slices of provolone and 2 slices of mozzarella.
Place open-faced pizza fold sandwiches into a 375° F oven and bake until cheese melts.
Remove from oven arrange the peppers on the cheese, place on plate. Serve immediately.