Upload user name and roles in CSV to give access to private area

We have a requirement where we need to give a list of users(about 1000) access to a private area. Many of these users are not regular forum users, so they will need to be processed in a way that allows for their permissions to be granted upon first visit to the forums. So, can I create and upload the CSV with their User name and Role? Would it work? 

Moreover, many of the users in our list have only e-mail IDs, can this CSV contain email-id,role or is it only username,role in the CSV.

Thanks