In a way similar to Google Calendar: How to quickly make several duplicates of an event?, I need to make many copies of events. However, it is important that they remain individual events (not part of a series), and so the answer to that question isn't appropriate.
I need them to be individual events because many people will have access to this calendar and will be able to change events. The calendar holds a rota, saying who is doing what, when. Everyone on the rota is free to arrange their own swaps, but I know from experience that if you allow a wide group of people edit on repeating events, it is easy for the whole series to be changed by accident. So I want each event to be an individual.