1. Bring the leg of lamb to room temp. Take the leg of lamb out of the refrigerator and leave it at room temperature for about 1 hour. 
2. Preheat oven to 450 degrees F. 
3. Using paper towels, pat the lamb dry. Using a sharp knife, score the top side of the lamb by making shallow cuts in a diamond pattern.
4. In a small bowl, mix minced garlic, olive oil, rosemary, thyme, Dijon mustard, kosher salt, and black pepper to create a flavorful marinade.
5. Rub the marinade all over the leg of lamb- massaging extra into the fat-scored part. Make sure to coat the lamb thoroughly for maximum flavor.
6. Place the lamb on a rack, fat side up, in a roasting pan. The rack allows the heat to circulate evenly around the lamb, promoting even cooking.
7. Pour the water and the red wine into the bottom of the roasting pan. This helps keep the lamb moist during cooking and provides the base for your gravy.
8. Roast the leg of lamb in the preheated oven. Roast for 10-15 minutes at 450 degrees F, then reduce the temperature to 325 degrees F. Cook for about 1 hour and 15 minutes more (see notes for doness guide). 
9. Baste the lamb with pan juices every 20-30 minutes to moisten it.
10. Use a meat thermometer to check the internal temperature of the lamb, which is about 125 degrees for medium-rare. Once the desired doneness is reached, remove the lamb from the oven, cover it loosely with foil,  and let it rest for 15-20 minutes before carving (the lamb will continue to cook as it rests, called carry-over cooking, and its internal temperature will continue to rise to around 135 degrees F). 
11. While the lamb rests, you can use the pan drippings to make a delicious gravy. Strain the drippings, remove excess fat, and whisk in 2 tablespoons of flour or cornstarch to thicken on the stovetop.
12. Carve the leg of lamb and serve with the homemade gravy.

Enjoy your perfectly roasted leg of lamb!