Hi, this text mode is for a collection of project users on a project. A "listdelimiter" is the separation between your results, when you have more than one result, as is normal for a collection.
In an assignment report, you do have the ability to only have one result (each assignment is made to a single user, and you have the ability to report on the role of that assignment), so a collection column isn't necessary, unless for some reason your goal is still to list the rest of the project team per assignment.
And, while it's possible to set up something that would indicate the role of the assignment in a column, it's just as easy (easier?) to simply filter for the 8 roles that you want.
Can you clarify what you're looking for in this particular assignment report? i.e. are you pulling in unrelated assignments and thus need to only display specific roles? Otherwise, maybe it's enough to filter and then group by the role with no text mode needed?