Preheat the oven to 400°F.
Remove any giblets from inside the chicken, pat dry and arrange on a roasting pan. Rub with olive oil, salt pepper and lemon juice, including in the cavity. Roast for 90 minutes, or 20 minutes per pound, until cooked through, golden and juicy.
Add all of the salsa verde ingredients except the oil to a blender and purée until smooth. With the motor running, drizzle in the oil to emulsify. Season with salt and pepper.
Let the chicken rest for 10 minutes before slicing and serving with salsa verde and lemon slices on the side.