I accidentally discovered this while experimenting. You have to set the Automation on whichever speed you're starting with. In other words, if the organ part with Rotor effect begins in SLOW speed, then THAT is what you set your automation on. If you start the part on FAST speed, THAT'S where you click for the Automation. Then, by moving the insert points up or down, the Rotor speed will change. You can't control the "ramp-up" or "ramp-down" of the speed, but you can at least change it.