How to Make It
Preheat the oven to 500° for 30 minutes. Let the leg of lamb stand at room temperature while the oven heats. In a mini food processor, pulse the rosemary, thyme and garlic until minced. Add the mustard, olive oil and honey and pulse to blend. Season the herb mustard with salt and pepper.
On a work surface, open up the leg of lamb and season it generously with salt and pepper, rubbing them into the meat. Spread 1 tablespoon of the herb mustard all over the inside of the lamb. Roll up the meat and tie at 1-inch intervals with kitchen string. Generously season the outside of the lamb roast with salt, rubbing it into the meat, then rub the lamb roast with the remaining herb mustard.
Set the lamb on a wire rack in a roasting pan. Add 1 cup of water to the pan. Turn down the oven to 375° and roast the lamb for about 1 1/2 hours, until an instant-read thermometer inserted in the center of the meat registers 130°; it should register 150° near the bone. Let the lamb rest for 15 minutes, then remove the string, slice and serve.