I have to say that I like your questions. They keep me thinking out of my box. Please give me more! 😉
But to answer this one:
Part 1: Unfortunately, I think there is absolutely no way to see when it was assigned. We can track the last modified date for many things, but not for the affected link table User_Pob_Role.
I already played with a History trigger based on a CollectionChanged Condition, but the PQL [AddedItem.Id] (nor [AddedItem.Description]) didn’t work there. If you require it, you should ask Wendia Support. IMHO, it is even a bug that [AddedItem.<column>] doesn’t work if you use it for an EM based table like PobRole. Do you know how to contact them and what to write? I would be interested in their answer as well.
Regarding the “who and which one”, please have a look back at my SQL statements on the other thread. Did you find someone to help you with the DB query?
If you need a more comfortable way within the GUI, you may need to open an RFC to Wendia.