Hello Samir Vaidya,
In order to redirect anonymous users to the login page, everytime they try to access a forbidden page, you will have to customize the "403 HTTP error" that is received by the user. This can be done by going to the web.config file of your application and adding the following code under the <customErrors> tag (your_login_page_url is the url of the desired redirect page):
Creating the "Public" role for publicly authenticated users is a good decision, although there is a built-in "authenticated" role that is applied to every user by default. So - if you don't want them to have any permissions besides viewing the page, you should simply not set any role to them (they would be just "authenticated" by default.
Hope that helps.
the Telerik team
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