Mix the ground beef with oats, 1 teaspoon of salt, pepper, and Italian seasoning. Once mixed thoroughly, roll out 16 meatballs. (If you are using a ground beef with less than 15% fat, you may want to add a bit of milk or cream to the mixture if it feels dry and the meat does not form into meatballs.)
Dipping your fingers in a bit of water when you roll the meatballs will make the process easier and create a smooth texture to the exterior of the meatballs. Once you have rolled all the meatballs, set them aside. (See video for how to make the meatballs.)
Warm a frying pan (preferably non-stick) on medium heat and add the meatballs to the pan. (If you are using a ground beef with less than 15% fat, you may want to add a bit of olive oil to the pan before adding the meatballs.)
Brown the meatballs. Once browned, add the diced tomatoes and tomato sauce to the frying pan and allow the meatballs to simmer in the sauce for approximately 20 minutes. This allows the meatballs to cook through completely.
While the meatballs are simmering in the sauce, bring a large stockpot with water to a boil. Once the water boils, toss the remaining teaspoon of salt into the stockpot. Add the spaghetti and cook according to package directions until al dente. (See video for a discussion of al dente.)
Once the spaghetti is cooked, drain the water and place the spaghetti into a large serving bowl. Top the spaghetti with the meatballs and sauce. Serve.
Leftovers can be stored in the refrigerator, well wrapped, for 3-4 days. Rewarm in a frying pan on the stovetop.