Heat the grill, and cook the sausages for 10-12 mins or until cooked through and golden brown.
Meanwhile, heat the oil in a small frying pan, cook the onion for 6-8 mins until soft, then add the garlic and cook for 1 min. Set aside.
Bring a pan of water to the boil and cook the broccoli for 3-4 mins until tender but still with a bite. Lift out using a slotted spoon and set aside.
Add the pasta to the water you have just cooked the broccoli in and cook following pack instructions. Drain well and return to the pan.
Chop the sausages into 2cm pieces and toss with the pasta, then chop the broccoli roughly and add to the pasta along with the cooked onions, garlic, chilli flakes, and lemon zest and juice. Toss everything together well with the rocket and season.