Lemon, Rosemary, and Garlic Slow Cooker Chicken

For the vegetables:

carrots, peeled and cut into thirds

medium onions, peeled and cut into wedges

medium red potatoes, cut into chunks

garlic cloves, peeled

For the chicken:

lemon, zested and halved

chopped fresh rosemary plus 3 sprigs

garlic clove, chopped

olive oil

to 5 pound whole chicken, rinsed and patted dry with giblets removed

Salt and freshly ground black pepper