Bring the broth to a boil; lower the heat to a simmer. In a large, heavy-gauge saucepan over medium-high heat, melt the butter. Stir in the rice, toasting just until it starts to sizzle and pop, about 1 minute. It should not color. Add the sausage and garlic. Stir, breaking up the meat into small bits, until the sausage has lost its pink color, about 1 minute. Pour in the wine.
Stir occasionally, cooking until the liquid is almost gone, about 2 minutes. Add just enough hot broth to cover the rice. Lower the heat to maintain a vigorous simmer; stir occasionally. When the liquid is almost gone, add just enough hot broth to cover the rice, along with a pinch of salt and cayenne. Check the risotto every 3 or 4 minutes, giving it an occasional stir to make sure it isn't sticking to the bottom of the pan and adding just enough broth to cover the rice when the liquid has almost disappeared. After a couple of additions of broth, add the broccoli raab.
Continue adding broth and checking until the rice is just al dente, about 20 minutes total cooking time. Bite into a grain; you should see a small white pin-dot in the center. Take the risotto off the heat and stir vigorously for a few seconds. Fold in the pepper, cheese, and a pinch of salt if needed. Stir in a few tablespoons of broth to loosen the risotto, if you like. Serve immediately.