Is there a way to assign a custom theme/skin to every role from the administration?

We can allow user to change his theme from Host->Permissions->Allow User Change Theme

How to implement it per role.

Thanks,

Joe

At this time you can't do this. In a future version of YAF they might put this option in, You can change the skins on how each of the forums looks. But you can't change the skin based on the role.