This guy may have wanted to spend his high dancing nonstop at a rave, but instead he ended up rolling in the back of a cop car.
“Rolling” is slang for being high on MDMA. The psychoactive substance in his system just wouldn’t allow him (or his face) to sit still.
In a social environment, users generally react to this class-A drug by having a deep sense of connection with those around them, or dancing with total abandon. In the back of a cop car, things are much different.
Just another reason not to do drugs, folks.