Bring the lamb out of the fridge and allow to come to room temputure 30 to 45 minutes before roasting.
If roasting with the vegeatables, toss them with the extra marinade and lay in the bottom of a 9 by 13 roasting pan, I use my cast iron. Place the lamb on top of the vegeatables.
If not using the vegeatables place the lamb on a rack.
Place the lamb in a 450° oven and roast the lamb for 15 minutes, then turn the heat down to 350°. Cook the lamb until the center of the lamb achieves 125. Use an oven-safe digital thermometer or check with an instant-read thermometer during cooking to get the temp just right. The lamb should take about 15-20 minutes per pound to cook.
For rare: 125℉, about 15 minutes per poundFor medium-rare: 130-135℉, about 20 minutes per poundFor medium: 135-140℉, about 25 minutes per poundFor well-done: 155-160℉, about 30 minutes per pound
Remove the pan from the oven. Loosely tent with foil and rest for 15-20 minutes before slicing and serving. As the lamb rests, the temperature will continue to increase the final 5-10 degrees to medium rare.
If cooking with the potatoes place them back into the oven durring resting time to crisp up if nessasary.
Slice the rested leg of lamb against the grain. Arrange the slices on a serving platter alongside the roasted potatoes and carrots.Drizzle with Demi Glaze:** Pour the red wine demi glaze over the lamb and serve immediately.