You can't rollback a step as this would require that the K2 server keep every activity into a long running transaction state.

 However, we normally work around it by providing a return action/outcome line to the previous activity as needed.

Thanks for your fast reply.

The thing is that i found a rollback method in the smart objects which confused me alot.

If you are talking about rollback in SmartObjects, it probably is referring to the COM+ transaction context.

This is because you can execute 1 or more service method calls inside the SmartObject method.  So you can control the transactional context across the calls.

i.e. Rollback, Stop or Continue.