A thing I do with a butterflyed leg is to get the oven pre-heated to 450. I sear the spread leg briefly on the griddle, then put it right on the oven rack with some vegetables to be roasted in a pan underneath. I usually marinade for about 4 hours, usually with some garlic, lemon, rosemary, crushed cumin seeds, ancho or guajillo chile paste, and some red wine. But I prefer bone-in.