Ooff, don't bother stuffing it at all. Throw in a halved clove of garlic, a few sprigs of fresh thyme and rosemary, truss, season and roast. Cook your veggies seperately. Don't stuff it with the spinach for sure.
I would suggest making a salad from the fresh spinach, then a saute of the eggplant and broccoli with the seasonings of your choice, and the chicken as described.