If your rolling contact fatigue model is implemented in another language, like C, FORTRAN or MATLAB, you should be able to call it from an S-function in Simulink.
If it is a general mathematical model consisting of ordinary differential equations, you should be able to model it in Simulink. You can also solve Index 1 Differential Algebraic Equations (DAEs) using Simulink with algebraic loops that impose constraints.
Contact dynamics often involve mode switching. This can be implemented using conditionally executed subsystems or for complicated logic, Stateflow. Good luck!
