Using a recent continuum model of a single-crystal nanowire morphological evolution in the applied axial electric field, an axisymmetric evolution of a microscopically rough nanowire surface is computed. Morphological evolution results in a wire breakup into a cylindrical segments (particles). Breakup time and the number of particles are characterized for various levels of the radial and axial surface roughness. It is shown that electromigration and larger surface roughness lead to a shorter breakup time and the increased number of particles.