Abstarct: Abstract The deformability of rock mass is an important issue that is always considered as an effective factor in the design of rock structures. Deformability is influenced by the characteristics of natural discontinuities in the rock mass and the characteristics of discontinuities are affected by their geometry and roughness. Given that in existing Discrete Fracture Network (DFN) models, discontinuities are simplified as planes, it seems necessary to construct a DFN model with rough joints that can estimate rock mass characteristics, including its deformability, by applying conditions close to real rock mass conditions. In this research, initially, roughness was investigated at two scales of field and laboratory and the order of arrangement of Barton’s ten profiles, which is the basis for determining the amount of roughness in terms of JRC, was evaluated. The results show that the fourth profile is rougher than the fifth, the seventh profile is rougher than the eighth, and the ninth profile is rougher than the tenth. baxsed on this, a change in the order of arrangement of Barton’s ten profiles from low to high roughness has been suggested. To simulate roughness, firstly, the amount of roughness was simulated. For this purpose, using the Kernel method, the probability distribution function of roughness was estimated and then using the combination method, a relationship for simulating the amount of roughness was proposed. This method has been validated by t-test, Levene's test, Kolmogorov-Smirnov and Mood tests. The Kernel method has also been suggested and validated for simulating other features of rock mass joints. After simulating the amount of roughness by presenting the DRS method, the geometry of roughness was simulated. The DRS method has been invented and developed baxsed on Barton’s field estimation method of roughness. In this method, the amount of roughness is determined baxsed on the length of field profile and the distance between maximum and minimum peak and toe points. The DRS method has been examined for validity and reliability by Mean Absolute Percentage Error index in two methods. Finally, to add roughness to discrete fracture network, a all procedures have been added as a subroutine to DFN-FRAC3D computer program. The simulation of roughness has caused the surface of the joints to break. This issue has made the construction of a real numerical model for investigating the deformability of rock mass very difficult, so much so that the execution time of the real model increases to the extent that it is not possible to run the real model. Therefore, in order to investigate the effect of roughness on the deformability of rock mass, six hundred and sixty numerical models with simulation of joint roughness have been built and analyzed in FLAC software. The results indicate that the smaller the angle between the discontinuity plane and the maximum principal stress plane, the more noticeable is the effect of roughness on deformability. So much so that with an increase in roughness values, the deformability of rock mass also increases to some extent.