Add the chicken broth, tomato sauce, garlic salt, and Italian seasoning to a large soup pot (~6 Qt). Add enough water to fill the rest of the pot 2/3 full. Place on the stove top on high and bring to a boil.
Cut the Hillshire sausage up into half inch disks. Add to the soup pot while bringing it to a boil. Once the broth is boiling, turn heat down, cover, and simmer.
The soup should simmer for a minimum of twenty minutes or up to 5 hours. The longer it simmers, the better the flavor.
Twenty minutes before you are ready to eat, bring broth back up to a boil and add the spaghetti. Once the pasta is tender (10 to 15 minutes) soup is ready to serve.