In this paper, effective fabrication of high-resolution diffractive optical elements on a polymer substrate is demonstrated using roller nanoimprint lithography. A nanoscale diffraction grating mold, which can generate a random laser pattern, is fabricated by scan-and-repeat projection lithography. The mold is imprinted to a thin polymer on the soft substrate via roller nanoimprint lithography, which has high efficiency, high fidelity, and high throughput for mass production. This fabrication process can produce high-resolution nanostructures while reducing the cost substantially. We obtained large-area polymer diffractive optical elements with a flexible substrate, which can generate high-quality diffraction random lattice patterns with sub-250 nm resolution for an 808-nm wavelength laser. The diffractive optical elements have about 83.2% diffraction efficiency and 99.7% uniformity of random pattern intensity. It is believed that this fabrication technique can promote practical applications of diffractive optical elements, such as laser wavefront correction, face and activity recognition, and optical communication. © 2020 Author(s).