A modular roller hemming system having a base assembly, a replaceable anvil, a spider arm assembly, a plurality of support arms for supporting the spider arm assembly, and a plurality of repositionable unit tools. The anvil is 3-D printed of a polymer composite material and may be replaced with similarly manufactured anvils having different form factors for receiving various shaped and dimensioned workpiece assemblies. The plurality of support arms are repositionable on the base assembly, the spider arm assembly is reconfigurable, and the plurality of unit tools are moveable to accommodate various anvils having different form factors. The support arms includes an upper segment that is detachable from the lower segment to facilitate the changeover of anvils.