My mother owns a roarer. He has roared basically his whole life, and has been evaluated by veterinarians. Because of other medical conditions (ringbone) he will never be used hard enough that the roaring will cause any breathing restrictions, so the surgery has never been performed on him.
And in warm-up rings, everyone knows when she's coming up behind them!
In my youth I also knew a horse that roared, had a surgery to correct it and was fine.
It really is up to you and your vet deciding what the horse is worth and whether the surgery is necessary to the horse's quality of life. If you have the means, really love the horse and your vet thinks he is a good candidate for surgery, then I would do it. If you are going to struggle to pay for it, or your vet thinks he won't pull through and his quality of life will suffer extremely (even being a pasture puff) then your best option may be humane euthanasia.