This isn't adding up for me.
A "Linked" field is one that travels up through a dropdown relationship and grabs a field in the parent table.
For example, I could make a table "Widget", where widgets are assigned to customers.
WidgetName (Text)
Customer (Dropdown)
If I wanted the CompanyName of the customer to show up in my Widget table, I would add a Linked field, via the Customer dropdown, that would grab it. So I would get:
WidgetName (Text)
Customer (Dropdown)
CompanyName (Linked - Via Customer).
So, in your example, you have RoleName and Vendor as Linked fields. But what are they linking via?
Or is this just terminology, where by "Link" you mean Dropdown? If so, setting the Vendor in the AssignmentTable by the Vendor's FullName will work.
Paul