If you specifically want to use AddStatement method with the signature in your example do it like:
var statement = routine.AddStatement(typeof(IJointMotionStatement), false);
P.S In your example, you create an empty component. So, instead of finding robot executor you have to create one (createBehavior -method) or (preferred) find a robot in the layout that has the executor already and work with that. See a simple example of finding first component in the world having a RobotController behavior.