Heat butter and olive oil together with onion and garlic in a large pot over medium heat; cook and stir ground beef and sausage in the onion mixture until browned and crumbly, 10 to 15 minutes. Stir Italian seasoning, salt, rosemary, oregano, and black pepper into ground beef-sausage mixture; simmer for 20 minutes.

Pour water, tomato puree, and tomato paste into ground beef-sausage mixture; simmer, stirring occasionally, over low heat until flavors have combined, at least 2 hours.