Wash the vegetables. Cut the bottoms off the broccoli rabe and set aside. Cut the peppers into 1 1/2 inch thick strips and set aside. Peel the onion and cut into 1/2 inch pieces and set aside. Peel the sweet potato and cube (about 1 inch by 1 inch). Remove the bottom of the Brussel sprouts and halve.
On a baking sheet lined with parchment paper arrange a bed of broccoli rabe. Place the peppers, onions, sweet potato, Brussel sprouts and sausage on top. Season everything with rosemary, fennel seeds, salt, pepper, garlic powder and olive oil. Give it all a toss.
Bake for 45 minutes or until the sausages have browned and the vegetables are tender.