You can use @UserRoles and @UserName in a HideWhen of a shared view action button. This portion of the view is not stored on the server; it is only generated when a user opens a view.
For selection formulas, you cannot use @UserName because the view is generated by the server and the server is the user. Use Private On First Use if you have to make view selections dependent on the user name; private views are stored in the user's desktop.dsk file.