Symptoms
Diagnoses
Resolution
Confirmed and logged as a bug in K2 Blackpearl 4.7. There are currently two viable options for workarounds. One is to not assign the role directly to the workflow, but rather to let that happen automatically by only selecting the role as a destination for an event and letting the role automatically get added when the workflow is deployed/actioned. The other is to use the Management features within K2 Workspace rather than the Management Site for adding roles to workflows.