Explicit formula connecting roughness profile of an electrode with the distribution of the electric field at its surface is derived for the case of smooth roughness, when typical height of roughness element is small in comparison to its size across a surface. An efficient numerical method is suggested for the calculation of the field distribution at the surface of very rough electrode. This gives us a possibility to calculate various injection properties of the electrode for a particular kind of injection rate: integral injection rate, surface distribution of injection peaks etc. It is shown also that rough surface of electrodes generates an additional energy disorder in the bulk of transport layer. This principal result indicates that electrode roughness affects not only carrier injection but carrier transport as well.