The paper proposes a method for the geometric calculation of cycloid gears for a harmonic drive system with supportive shaped rollers. The results are validated through computer modeling of outer and inner cycloidal rings geometry in a computer-aided design system. The computer modeling yields 3D models of the inner and outer cycloidal rings through geometric subtraction of surfaces by moving sections and transitions between them. The advantages and disadvantages of the 3D models are identified. Possible solutions for eliminating the shortcomings are suggested. The developments can be used for designing general industrial gearboxes or gear mechanisms for robotics, aerospace, oil and gas and other industries, as well as in the development of control programmes for the manufacture of cycloidal rings. This calculation and computer modeling method can serve as a useful recommendation in the design of harmonic drives with supportive rollers.