Rather than insisting players pay attention at all times, or scroll back through the logs to discover, have some visual indicator to show who picked the role currently being performed. We have the governor's icon to at-a-glance show who is the governor; we should also have at at-glance mechanism to show who picked builder, etc.
My recommendation for such a mechanism would be to, in addition to striking out the role as it is now, instead of colorizing it grey, colorize the role name with the player color of the person who chose it.
My recommendation for such a mechanism would be to, in addition to striking out the role as it is now, instead of colorizing it grey, colorize the role name with the player color of the person who chose it.