Preheat the oven to 350 degrees and spray a 9x13 deep baking dish with non-stick cooking spray.
In a large pot, bring water to a boil over medium high heat. Cook pasta according to package directions for al dente.
Save ½ cup of pasta water, set aside. Drain the remaining water and return to the pot.
In a large skillet, melt butter over medium heat.
Add sausage links and cook until all sides have browned.
Remove from the skillet, and when cool enough to handle, slice into ½-inch slices.
In the same skillet, add the meatballs and brown on all sides. Remove.
Return the sausage to the pan and add diced bell pepper and onions. Cook until the veggies are tender.
Add tomato sauce, tomato paste, pasta water, oregano, basil, garlic powder, pepper, and red pepper flakes. Stir to combine and cook over medium heat for 20 minutes.
Add meatballs to pan and stir to combine. Continue cooking for 10 minutes.
Add pasta, stir to combine, and pour half of the mixture into the prepared baking dish.
Sprinkle half the mozzarella cheese next, followed by the remaining mixture.
Add the Parmesan cheese and then add the remaining mozzarella cheese on top.
Cover with aluminum foil and bake for 30 minutes or until the cheese is hot and bubbly.
Carefully remove from the oven and enjoy with a side salad and crusty bread.