The use of the roll is rolling mill ,
where the Steel plates is used to make thinner steel sheet rolls as below image
So basically it's main raw material of any steel user industry as roller and shaper need to give desired shape to steel to make any end user product like vehicle chassis (car , bus , truck) , industrial machines and heavy machineries
This is very technical manufacturing as you have to assure full quality of meterial.
This roller will be used at 1000 °C temperature with so much stress and pressure.
So no industry will use lesser quality roller and customer will only order to same and reliable manufacturers whom they trust so deem roll will get repeated order from customer in this case.