Spray a shallow casserole dish or 9x13-inch pan with olive oil spray and set aside. Heat oven to 425.
Cut the bell peppers in halves lengthwise. With a small, sharp knife cut away the stems and remove the seeds and membranes. Put into the pan and set aside.
Cut the chicken into pieces and drop into a food processor to grind finely. Transfer to a bowl and set aside.
Defrost the spinach and squeeze out the excess moisture. Add to the chicken.
Spray a large, nonstick skillet with olive oil spray, place over medium heat. Add the onion, garlic and a tablespoon of water. Saute 4 minutes. Add to chicken mixture. Add the crumbs, fresh rosemary or dried basil, salt, pepper, roasted pepper, parsley and egg white. Mix with clean hands to blend. Spoon into the cavities of the peppers. Spoon the marinara on top and around the peppers. Cover tightly with aluminum foil.
Bake 35 minutes. Uncover and sprinkle with the cheese. Continue baking 5 minutes or until the meat is cooked through. (Peppers should be tender when pierced with a knife.) Let sit 5 minutes before serving.