Bake for about 1 hour and 10 minutes for rare doneness or until a thermometer inserted into the centre of the meat, without touching the bone, reads 122°F (50°C). Set the lamb aside on a plate, cover with aluminum foil and let rest for 15 to 20 minutes or until the internal temperature reaches 135°F (57°C). Remove the twine. Continue cooking the vegetables while the meat rests.
Herb Sauce
In a food processor, chop the herbs, green onion, garlic and chili pepper. Add the oil and vinegar. Season with salt and pepper. Pulse until just coarse. Set aside in a bowl.
Slice the leg of lamb. On a serving plate, place the meat and vegetables. Dress with half of the sauce and serve with the remaining sauce.