ok, had a good look at the manual on my phone under the roof section. there is a separate roof control module, this module has outputs to the motors, inputs from various limit switches.
most importantly; it requires the brake to be pressed, the ign to be on, the car speed to be under 2mph, the battery voltage is above 10v
the speed signal is a pulse input which would need simulated, the brake signal also needs to be faked.
this is possible but needs a payback module for the roof to be made, I don't have a roadster to develop it on sadly.