In a large skillet over medium heat, saute the onion until translucent in a few tablespoons of olive oil. Add the sausage and cook until pink has faded. Add the wine, vegetable cube (dissolved in a cup of water), salt, and pepper.
Reduce to low and simmer for 2 hours, stirring regularly. When only a few minutes of cooking time remain, dissolve the saffron in 1/2 cup water and add to sausage mixture.
Meanwhile, bring a large pot of salted water to a boil. Cook the pasta until al dente and drain, reserving some of the cooking water.
Add the pasta to the sausage mixture, and then mix in rosemary. Add some cooking water if it seems dry. Serve immediately with a sprinkle of Parmigiano.