Preheat the oven to 190°C, 170°C Fan, Gas Mark
In a small bowl mix together the orange zest, juice and garlic together.
Put the vegetables, except the broccoli in a large non-stick roasting tin, season and spoon half the citrus mixture over the vegetables. Toss lightly.
Lightly score the surface of the lamb joint, stud with the rosemary leaves, season well and position on top of the vegetables. Roast uncovered for 1-1½ hours or depending on how you like your lamb. Cover with foil, if browning too quickly.
Remove the roasting tin from the oven and remove the joint. Transfer to a warm plate, cover with foil and leave to rest for 15-20 minutes.
Add the broccoli around the vegetables and spoon over the remaining citrus mixture. Return to the oven and roast uncovered for a further 15-20 minutes.
Remove the vegetables from the oven. Lightly crush the potatoes.
Carve the lamb into thin slices and serve with the remaining roasted vegetables, garnished with freshly chopped parsley and any meat juices from the pan.
