In large skillet, brown sausages on both sides until thoroughly cooked. Remove from pan. Saute onions, peppers, mushrooms and garlic in olive oil over medium heat until they start to soften, 3 minutes.
Slice sausages into 1/4 inch coins and add back into pan. Pour in tomatoes, stock and seasonings. Cover and simmer 20-30 minutes. In the mean time, boil water and cook pasta.
Spoon cooked pasta into serving bowl, top with sausage cacciatore and parmesan cheese, if desired.