Cook the pancetta in a large pot over medium heat, stirring, until slightly crisp, about 5 minutes. Meanwhile, rinse the turkey giblets; chop into 1/2-inch pieces. Add the giblets and neck to the pot; cook until browned, about 5 minutes. Add the onion and red pepper flakes; cook until the onion is soft, about 3 minutes. Stir in the tomato paste, garlic, bay leaves, rosemary and 1 teaspoon salt; cook, stirring, about 5 more minutes.
Add the wine and cook until slightly reduced, about 5 minutes. Crush the tomatoes into the pot with your hands and pour in the juice from the cans. Add 3 cups water and the parmesan rind, if using. Increase the heat to high, bring to a boil and cook 5 minutes. Stir, then reduce the heat to low. Partially cover and simmer, stirring occasionally, until the meat is falling off the neck bone, 4 to 5 hours.
Remove the neck; pull the meat off the bone, shred and return the meat to the sauce. Remove the bay leaves. Stir in the parsley; season with salt and pepper.
Bring a pot of salted water to a boil; add the pasta and cook as the label directs. Drain and toss with the sauce. Top with shaved parmesan.