Users and roles should be created in the system level. You may assign users to one or more websites.
Add new users
When creating a new user you can set the ui culture for the user. It represents the language of the admin interface.
When you select a language a new localization file will be created in the I18N folder, which you can then translate into your language.
Add New roles
After creating users, you can also add some roles to the system. Each role contains a permission setting that defines what area the role has access to.
Assign users with roles to a website