In a toaster-oven baking tray, combine the chicken, 2 tablespoons of the oil, the salt, pepper, rosemary, and sliced garlic. (You can cover and refrigerate for up to 12 hours.)
Spread in a single layer, skin-side up, and roast until cooked through, about 35 minutes.
Meanwhile, in a small bowl, combine the olives, tomatoes (if using), chopped garlic, parsley, and the remaining oil. To serve, divide the greens and chicken among individual plates and spoon the olive relish over the top of both.