I haven't been able to find the keyed shaft, are you talking about the one Swagoffroad makes?They work ok. If you try to roll tube thats too thick the rollers are going to slip on the drive axle. There is a company that makes a new axle that is keyed and makes different size rollers.
Did your rollers strip out? If so, how did you fix it? Larger set screws or?I used one to build my engine stand and shroud. the shaft it comes with is keyed. However the bolt holes in the rollers will strip out. its not the shaft thats the problem. It will also corkscrew all the bends.