I worked for a marina many years ago, and they wouldn't touch a roller and cable system. If a cable bound, a roller cracked or snapped off at the swivel, or a number of other things happened, they didn't want to bear any responsibility for someone's injury or death. We either swapped them out or refused the business. Since then, I have stuck to that reasoning. I won't touch them either.
A NFB rotary steering system is what I put in almost every boat, all of mine, to be sure. Truthfully, if you get your motor the right depth, and set the trim tab above the prop just right, the boat may track straight, but it's SO much better with NFB.
Just do it. Absolutely worth it, if for no other reason than safety.
And for what it's worth, I've removed numerous pulley systems from boats, and sometimes they are in great shape, and sometimes they were very close to or already in failure condition. Things like that never break at a good time. I will probably happen during times of maximum stress, like when running at full speed and you go to avoid another boat, and <snap> now you can't steer, or worse yet, the boat suddenly lurches off to one side or another. It happens really fast, and people can die that way. So IF you decide to keep the roller system, remove and check every roller and cable clamp regularly.