I can’t reproduce this at the moment but I have seen that exact error in other parts of the admin console. I’ll open an issue for this and try to get to the bottom of it.
Does this happen every time you try to set a role? Were your roles set to policy defined before you upgraded or did you have other roles defined for identities?
Can you do me a favor and open the development tools in your browser (F12 usually) and then cause this error to happen? In the console it should show and error with a stack trace you can expand. I’m just wondering if it will provide the decompiled names of the methods so I can trace this a bit better.
I’ve been seeing that page show up throughout the Admin console settings pages when my session times out. if i refresh it forces login and then it’s fine. Hope this helps some.