Preheat your oven to 375°F.
In a small bowl, combine the minced garlic, chopped rosemary, chopped thyme, olive oil, Dijon mustard, salt, black pepper, lemon zest, and lemon juice to create a herb paste.
Place the leg of lamb in a roasting pan. Rub the herb paste all over the lamb, ensuring it’s evenly coated.
Roast the lamb in the preheated oven for about 1 hour and 15 minutes for medium-rare, or until the internal temperature reaches 135°F. Use a meat thermometer for accuracy.
Remove the lamb from the oven and let it rest for 15 minutes before slicing. This allows the juices to redistribute.
Slice the lamb against the grain and serve with your favorite sides.