I'm not an expert, but I need to ask: are you talking about rolling over a payday loan? Or rollover of a retirement plan?
Anyway, in simple terms, to rollover a payment basically means to postpone it. When you have a loan to pay off, for instance, rolling off a payment means you will delay paying the loan off, but you'd have to pay a fee. That fee will NOT reduce the amount you need to pay (the installment) though! So, in other words, it's best to avoid doing it.