This paper develops a novel method to fabricate seamless and complicated patterns of microstructures onto the cylindrical surface of a metal roller. This patterned metal roller can then serve as a roller mold in roll-to-roll (R2R) continuous roller imprinting of microstructures at low-cost, high-speed, and large-area. The first step towards fabricating a seamless roller mold is a pneumatically driven and self-spinning coating method and system which can uniformly spin-coat a smooth thin photo-resist (PR) layer on the cylindrical surface of a roller. After the PR coating, a UV exposure system which consists of a UV light source, a mask, and a rotary mechanism is setup up so that the PR coating is exposed in a step-and-rotate manner. Finally the exposed PR on the surface of roller can be developed and then the metal roller can be chemically etched, similar to standard process in conventional photolithography. That completes the fabrication of seamless roller molds. A number of seamless roller molds with different patterns of microstructures have been successfully fabricated. Potential developments and possible applications are under investigation.