RF is limited in time travel by being unable to do anything that prevents Barry from becoming the Flash and being the Flash long enough to become hiss obsession. I'm gonna guess this show will stick to one of the more common time travel rules that you cannot change a moment in time if you know how it's supposed to play out, and doing so can cause a paradox.
So basically once Barry meets RF, he can't go to the future and stop him before he hurts anyone because it would alter Barry's past by getting rid of RF and mean Barry would never go to the future to stop him. Which would mean RF wouldn't have been stopped, and basically a paradox would be created. Though until we see the show address time travel we won't know, though I imagine they'll use similar rules to that if they ever want to do a Flashpoint inspired arc.