Set a 4-quart saucepan over medium-high heat and add the olive oil. Once hot, add the sausage to the pan and cook, stirring occasionally until well caramelized, about 5 minutes. Add the mushrooms, onions and peppers to the pan and cook for 7 to 8 minutes. Add the garlic and tomato paste to the pan and cook for 1 minute. Add the chopped tomatoes, juices, chicken stock and marjoram to the pan, and season with the salt. Bring to a boil, reduce the heat to a simmer, and cook until the flavors have married, about 20 minutes.