When you trade in your old car, the dealer or lender will normally pay off the remaining balance of your old loan by deducting it from your car’s trade-in value. If the trade-in value is higher than the remaining balance, you’ll receive a check for the difference.
With a rollover loan, though, the dealer or lender will take the remaining balance and roll it over into a new loan when you get your new car. While you’ll pay more in the long run due to added interest, you’ll still be able to get the new car you want without a hassle.