No ideas so far?
I guess I have to post the enhencement request on the JDev forum..
I have worked out a method myself.
I create a script that will contain the configuration items (such as the roles, privileges and oauth clients).
I capture the statements to create the items by defining them using the SQLDev REST Data Services dialogs and copy the resulting statements from the Statements log.
Then I create a script for every REST Module, again using the dialogs in SQLDev and capturing he statements from the log.
Once you have done this for one module with one template and a few handlers it is not difficult anymore to add more templates and handlers by writing the statements yourself.
This works if you have a relatively small number of templates and handlers, but might become tedious when having lots of them, so I hope some script generation and version control capabilities will be added to SQLDev.