Preheat the oven to 425°F (220°C).

Heat 1 tbsp olive oil in a Dutch oven over high heat.

Add the lamb roasts to the Dutch oven and brown on all sides.

Season the lamb with salt and pepper.

Place rosemary sprigs under the lamb roasts.

Add crushed garlic and red onion wedges to the pan.

Roast in the oven for 20 minutes, or until the lamb is cooked to your desired doneness.

Remove the lamb from the dish, cover, and let rest for 10 minutes.

In a separate shallow baking dish, place parsnips, carrots, and potatoes.

Toss the vegetables with the remaining 1 tbsp olive oil and scatter with chopped butter.

Roast the vegetables for about 30 minutes, or until tender and golden brown.

Increase oven temperature to the hottest setting during the last 10 minutes of vegetable roasting (after removing lamb).

Return the lamb baking dish to the stovetop over medium heat.

Add the flour to the pan and cook, stirring, until the mixture bubbles and is well browned.

Gradually stir in the chicken stock and bring to a boil, stirring constantly, until the gravy thickens.

Strain the gravy into a small pitcher.

Serve the sliced lamb roasts with the roasted vegetables, gravy, and steamed broccoli (optional).