This paper presents the design of a system for generating realistic problem instances for loading and unloading RoRo (roll-on roll-off)-ships in seaports. The generator can be configured according to problem-specific layouts and input data like the cargo types, stowage plan, size of the terminal areas and vessel, and distribution of specific travel times. Each thus generated instance represents a scenario in which a RoRo-ship arrives at the harbor to be loaded/unloaded. The resulting instances are viable inputs to test planning approaches and we shortly discuss their applications in static and dynamic decision-making.