This is a feature in the Customer Support add-on that lets you assign your tickets to users based on your rules.
Selecting a user
You can only select one user to assign your ticket to, and that user needs to have a Customer Support license. Note that only users with a Customer Support licence will be shown in this option.
Selecting a role
Roles can contain multiple users. If you select a role then Upsales will randomly pick a user inside of that role that has Customer Support license.
The user assigned to the ticket will see it in their ticket list.