CFDs are a leverage product and can involve a significant risk of loss. Trading CFDs may not be suitable for all, therefore you should ensure that you understand the risks involved and take into account your individual circumstances.
Trader's Glossary

What is Rollover?

In Forex trading a rollover occurs when a position is kept open overnight without it being settled (two days being the usual delivery date for Forex). For the position to remain open it must be closed and re-opened so that the scheduled delivery date is deferred for another day. Brokers automatically do this at the same price the position was initially opened at. Rollovers require a swap transaction to take place where the difference between interest due on the currency borrowed and due to the currency bought is settled.