Forum OpenACS Q&A: Re: Workflow "Rollback" Functionality?
If you're using the procs to get enabled actions to build a button-list or similar choice widget for user actions, the always_enabled_p states are returned along with the "properly defined" transition actions.
So this gives you an easy way to present the user a choice.
Now implementing the action properly is something else altogether and workflow will give you no help there. If the rollback action depends on the state you're rolling back to, then explicit transitions are probably the way to go...