You can hear the grunts of exertion and the shouts of call signs that foreshadow the use of a specific strategy. Quick-footed players run through walls of the opposing team, sometimes getting stopped cold, sometimes finding a hole to burst through, and sometimes dancing back-and-forth laterally in an elaborate game of chicken.

Now imagine there’s no ball.

And everyone is wearing roller skates.

That’s roller derby.

T...