Clean the chicken well and put in the crockpot breast side up. Stuff the garlic and the rosemary leaves between the skin and the breastmeat. Pour the bottle of french dressing over the chicken and cook on low for 6 - 8 hours. Serve with the sauce.
NB: I am having an increasingly difficult time finding tomato-based French dressing that has a hechsher that is not full of artificial sweeteners, HFCS or other garbage. I have had to resort to making my own. It is fast and easy to do - I just put the following ingredients right into the crockpot and make sure everything is completely mixed in: