This rad article touches on many things including this topic, but that's how living organisms are.. ridiculously complex and interconnected.

]http://barefacedtruth.com/2014/12/24/topical-antioxidants-protecting-skin-cellular-assassins/

Now it says you cant live without ROS because it is a catalyst for a bunch of bodily actions. But bodies are very adaptable, I bet it could adapt to not needing ROS, and instead feeding off straight free electrons- eat energy directly rather than eating food for a chemical reaction that creates free electrons. If you can live without ROS you would live for a very long time.
I've heard some people have developed the ability to not need to eat, not sure how that works, or if there is any scientific reasoning behind it, but im sure some can.. and some die trying.