In a mixing bowl, combine minced garlic, chopped rosemary, thyme, olive oil, lemon zest, kosher salt, and black pepper to create a fragrant herb paste.

Lightly score the surface of the bone-in leg of lamb in a diamond pattern and rub the aromatic herb paste into every crevice.

Place the herb-rubbed lamb in a large resealable bag or a covered dish, and marinate it in the fridge for at least 1 hour, ideally overnight.

Remove the marinated lamb from the refrigerator and let it sit at room temperature for about 30 minutes.

Preheat your oven to 350°F (175°C) for roasting.

Place the marinated lamb on a roasting rack inside a large roasting pan, and scatter baby potatoes around it, drizzling with olive oil and seasoning with salt and pepper.

Roast the lamb uncovered for about 1 hour and 45 minutes, or until the internal temperature reaches 135°F for medium-rare.

Carefully remove the roasted leg of lamb from the oven and tent it with aluminum foil. Let it rest for 20 minutes.

Slice the lamb into thick pieces, arrange on a platter, and drizzle with pan juices.