I've often wondered about that term ever since hearing it in The Blues
Brothers movie. The reference below is to the police car?

Elwood Blues has just passed on a red light, and a police car rolls up
behind them. The words are said in the same rhythm as a blues song ("Soothe
Me") on the car stereo]
Elwood Blues: ****!
Jake Blues: What?
Elwood Blues: Rollers...
Jake Blues: No!
Elwood Blues: Yeah.
Jake Blues: ****!