1. In a large, deep frying pan, heat the oil over moderate heat. Add the sausage and cook, turning, until browned and cooked through, about 10 minutes. Remove the sausage and, when it is cool enough to handle, cut it into 1/4-inch slices. Pour off all but 1 tablespoon fat from the pan.
2. Reduce the heat to moderately low. Add the onion to the pan and cook, stirring occasionally, until translucent, about 5 minutes. Add the garlic and cook 30 seconds longer.
3. Add the wine and bring to a simmer. Add the sausage, tomatoes, water, rosemary, red-pepper flakes, and 1/4 teaspoon of the salt and bring to a simmer. Cook, stirring occasionally, for 10 minutes. Stir in the parsley.
4. Meanwhile, in a large pot of boiling, salted water, cook the fusilli until just done, about 13 minutes. Drain and toss with the sauce, the ricotta, and the remaining 1/4 teaspoon salt.
Wine Recommendation: The acidity of the tomato and spiciness of the sausage are best suited to a red wine with soft tannin and good acidity. Try a sangiovese from Tuscany such as Chianti Classico or Rosso di Montalcino or look for a version from California.