ACL role assignments not showing on screen, but still working
Once I saw a second person report the same issue, I suspected a bug, so I successfully replicated the problem on the demo site.  See the CiviCRM bug reporting page.

I determined that this is a side effect of changes made in CRM-20351. 

Because this seemed like an easy enough bug to fix, I went ahead and did so.  I filed it as CRM-21076, and submitted a solution as pull request #10866.

It's a one-line fix, so feel free to fix manually.  I'm going to argue that this should go into 4.7.24, but 4.7.25 seems almost a certainty.