Step 1
Heat olive oil in a stockpot over medium-low heat; cook and stir garlic in the hot oil until lightly browned 1 to 2 minutes.
Step 2
Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly 5 to 7 minutes; drain and discard grease. Stir ground beef into garlic. Add crushed tomatoes and tomato puree to ground beef mixture; season with salt and pepper. Cover stockpot and simmer mixture stirring occasionally until flavors have blended about 2 hours.
Step 3
Heat a large skillet over medium-high heat. Cook sausage links in the hot skillet until browned and not longer pink in the center 10 to 15 minutes; drain and discard grease. Slice sausages into 1/4-inch rounds. Stir sausage green bell pepper and onion into the simmering tomato sauce; cook stirring occasionally until bell pepper and onion are softened about 1 hour.
Step 4
Preheat oven to 350 degrees F (175 degrees C).
Step 5
Bring a large pot of lightly salted water to a boil. Cook rigatoni in the boiling water stirring occasionally until cooked through but firm to the bite 10 to 11 minutes. Drain and return rigatoni to pot.
Step 6
Dice about 3/4 the mozzarella into 1/8-inch cubes. Mix cubed mozzarella with ricotta cheese in a bowl. Stir cheese mixture into cooked rigatoni until mozzarella cheese begins to melt. Pour rigatoni-cheese mixture into 2 large casserole dishes; add tomato-meat sauce. Toss well.
Step 7
Slice the remaining mozzarella cheese and arrange on top of rigatoni mixtures.
Step 8
Bake in the preheated oven until mozzarella cheese is melted and browned about 45 minutes.