I have the X45 with Rotary 1 and Rotary 2 set to trim pitch and roll. No problems with it.
Be sure to calibrate the axis when you set the rotaries AND to return them to the detent center position when calibrating. You want that center position for trim so you can adjust up/down, left/right.
Schatzi that might be why RPM works, but trim doesn't work for you. You most likely calibrated and sent the rotaries to the "Low" position rather than center.