Store & acess data in Business Objects

Hello,

I created in the Business Data Model 2 Business Objects, called BOCostumer and BORole.
=== BOCostumer ===
Name;Type;Multiple

name;STRING;NO
adress;STRING;NO
role;BORole;YES

===== BORole =====
Name;Type;Multiple

desc;STRING;NO

To store data I use a Service Task. First of all I have created Business Variables, called BVCostumer and BVRole. In the task I created a operation and filled in like the following:
BVCostumer --> setname --> "Testname"
BVCostumer --> setadress --> "Testadress"
BVRole --> setdesc --> "Test Description"

This workes fine, but I have problems to get a reference from the new Costumer to Role XY. Can I do this via a operation in Bonita or is it necessary to write it via script?
I need the data from the Business Objects in a task, so how to get them and save them to a pool varaible?

Thank you very much :)