If by login you actually mean the actual account creation, you might want to investigate the Auto Assign Role module:
The Auto Assign Role module serves three primary purposes. The first is to provide an automatic assignment of roles when a new account is created. The second is to allow the end user the option of choosing their own role or roles when they create their account. The third is to provide paths that will trigger a specific role when an account is created. The administrator has full control over these functions and can have them working together or independently of each other. Auto Assign Role is integrated with the Content Profile module so that you can have content types serving as registration pages. You can even replace the default user/register page with a customized version of your own design.
Otherwise, what @Molot mentioned previously is about it: Drupal doesn't rely upon where you login to generate roles for the user.