In Service Studio you can use roles that are exposed by another eSpace or extension, called, in this context, a Producer. Simply add these roles as eSpace reference of your eSpace, called, in this context, a Consumer eSpace.
How to add a Role reference:
Once roles are added as references, you can use them in your eSpace:
In any action flow, by dragging the role related action from the Role folder (on the Logic Layer of the eSpace Tree), into the flow, just like any other action or
How Role References are Executed
The role that you added as a reference is checked in the context of the Consumer eSpace, that is, within the same database transaction.
Add/Remove eSpace References | Expose a Role | About Platform Server Session