Fractures significantly influence fluid flow and mass transport in projects of radioactive waste disposal in deep geological formations. This work investigated the mechanism of nuclide migration in fractured rocks by considering fracture roughness based on a unified pipe-network method (UPM). The processes of adsorption and decay were incorporated into the UPM framework to capture the nuclide migration in a rock mass with rough-walled fracture networks. Benchmark tests were attempted against analytical results of the concentration distribution along a single fracture. An equivalent method to approach the hydraulic fracture aperture in fractured rocks by considering fracture roughness was also demonstrated. The influences of the fracture-roughness distribution, the rock matrix adsorption capacity and the transport properties on the process of nuclide migration were investigated. The results show that the breakthrough curve for the nuclide migration moved toward a longer time with increasing fracture roughness. The increased diffusion coefficient and retardation factor in the rock matrix greatly enhanced the matrix retardation effect on nuclide migration. Furthermore, the nuclide featured longer half-life results in a higher relative nuclide concentration of the domain. A hydraulic gradient with a relatively low value greatly impacted the relative concentration's distribution.