RORB does not explicitly model the pervious areas connected to drainage systems. What RORB allows you to do is to split a subarea into 3 separate surface types with a different set of losses for each surface type. When you split the subarea into the 3 different surface types, RORB treats the losses the same way for each surface type, it is just the IL and CL change depending on user input. This means that it is up to you to decide how to apply the losses.
When you mention pre-burst losses are you referring to the losses supplied by the ARR data hub? If you are then you are correct that they are designed to be used for pervious areas. There is some guidance in ARR Book 5 Chapter 3 in how to apply losses for the different surfaces but you would need to decide whether this is appropriate for your catchment.