We just uploaded a white paper on integrating Rollbase and OpenEdge Business Process Manager Applications.
This new white paper is available here.
This discusses calling Rollbase from worksteps in OE BPM, and having Rollbase call OE BPM to start new Business Processes, or continue worksteps.
I would note that with the release of Rollbase 2.0, and DataDirect Cloud, that there are additional options including calling the DDC Rollbase Data Source from the DBAdapter in BPM.