The CB1100 Community Forum

That means: let's rock! 

It's the riding mode. Other bikes have something like: rain - road - dynamic (or sport), the R18 has: rain - roll - rock. 

It controls the power delivery of the motor.

Rain mode is super soft. Switched to it by accident once and thought I was running on one cylinder beer mug. 
Roll mode is nice and smooth.
Rock mode is full power.

I always ride rock mode. I can ease off the throttle by myself, when it's getting diffficult. 

Reminds me of demo-riding the Verge electric motorcycle. If I recall correctly its modes were “chill” and “beast”. I could be wrong.

The first thing I think of when I think of something fast is a rock.

Well, think more of a rockslide.