Thanks for your query. There are several ways to set up a special storage in RORB. Typically, this is best done using an SQ table determined externally using a simple hydraulic calculation or a hydraulic model such as HEC-RAS. Alternatively, you can use the weir/pipe formulation within RORB to simulate the behaviour of various types of outlets.
In regards to a pump, you would need to incorporate this into an SQ table which was prepared externally.
Hope this helps.