Preheat the oven to 425°F.
For the sauce, in a large saucepot, combine the onions, olive oil, salt, and pepper and cook over medium heat until the onions brown. Add the bones and turn the heat down to low. Allow the bones to render for about 15 minutes while stirring occasionally.
In a large bowl, crush the peeled tomatoes by hand until they have a chunky consistency.
Add the crushed tomatoes and tomato purée to the pot and simmer for 2 hours, stirring every 5 minutes. Like we said, it’s a labor of love.
For the breadcrumbs, in a large bowl, toss all the ingredients together and combine well. These’ll keep, covered, in the fridge for about a week.
For the meatballs, Preheat the oven to 350°F. Line a rimmed baking pan with aluminum foil. Combine all the ingredients except the cooked sauce in a large bowl and mix with your hands, being careful not to overmix. If the mixture is too dry, add water in 1/4-cup increments. Roll the mixture into golf ball–size balls or ovals and place them in the lined baking pan. Add 1/4 cup water to the pan and carefully transfer to the oven. Bake for 1 hour, or until the meatballs are golden brown. Remove and set aside.
To make the rolls, place dough on a clean, flat, dry surface and stretch out evenly, using flour liberally to help spread the dough. You may use a rolling pin to spread the dough. Once the dough is round and roughly 16- to 18-inches in diameter, use a pizza wheel cutter to cut the round-shaped dough in 4 quarters. You should achieve 4 triangle-shaped doughs. Fill each piece with 16 meatball wedges along with 1 cup of cooked tomato sauce and 3/4 cup of Polly-O mozzarella cheese. Sprinkle a generous handful of Pecorino Romano cheese to top. Roll each dough up while keeping all of the ingredients inside of the dough.
In a large baking pan, add 1 cup of olive oil to bottom then place 4 meatball rolls on the pan. Cover the top of the meatball rolls with olive oil then sprinkle tops with a generous amount of sesame seeds. Place the rolls in the oven and bake until golden brown, about 12-15 minutes. Remove and cool before serving.