How do you roll back a digital speedometer in cars?

This is illegal to do. You would have to ship the odometer to the manufacturer to have this done. Doubtful they would do this as it is also illegal for them to do this, too. Your only recourse is to...

there is no way to roll back miles, its a pemenent memory even going in reverse will add miles to your bmw. be sides its illegal to tamper with any vehicle milage.

Drive slower, and the speedometer decreases. If you are asking how to (illegally) decrease the odometer's kilometer reading, then shame on you.

If your was repossed you need to call the car company and pay your car