Ed,
rolloff simulator does not actually use an external device, it provides the framework and simulates the action of opening and closing. I have a driver developed from the simulator that might proved a starting point for you to use.
github.com/wotalota/indi-rolloffino
There is a html sub-directory that provides and overview if you copy that to a local directory. It works via an Arduino controller, various versions of which are provide.
If you were thinking of directly using Raspberry Pi GPIO connections I have one that does that using pigpio but it is not yet fully debugged, it still has a timing issue at startup.
/Tom

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