Derivatives in terms of Margin and Expiry of the Rollover
A trader has to face Rollover usually in the Spot Forex markets. In future and options its usully already calculated when the price of future and options of a product is derived from its spot price.
Roll Over Can also be called as a interest rate differential. means its the cost of diffrences of the interest rate of different currencies.
Like if you r buying a currency against Dollar that has a lower interest rate then dollar then the bank with whome you are dealing through exchange will pay you the interest rate differance. But if you are buying a currency that has greater interest rate than Dollar then bank also charge you the interest rate differance on the overnight or per day baises.