I occasionally use "rolling" too. In the situation where I've been cleared for take-off, and having read back that clearance, but not able to go just yet for wake turbulence separation. (Intersection departures behind 737s are very common where I fly.) So I'm all lined up and cleared for take-off and when the wake turbulence wait periode is over, I call "rolling". I don't know what else to say, and a call like this seems to be appreciated by ATC anyway.
Technically I think I don't have to say anything though in that situation.