Did you buy the roller rockers as a separate rockers only?
It comes as a complete kit with shafts & pedestals, .. or at least mine & Ferals did.

The shaft needs to be hardened to run the roller bearings & if the rockers were designed to go on a standard [soft] shaft the rockers would need to be very large to accomodate the roller bearing. This would make them too large to correctly position the adjustment screw which is closer to the centerline of the shaft in order to get the increase in rocker arm ratio.