There are a few things to take into account when receiving errors uploading rosters:
Make sure there are no special characters or apostrophes in the email addresses, this will cause issues with the roster uploader.
Make sure there are no trailing spaces or leading spaces to any of the information in any cell, this has been known to result in an error as well.
Make sure that all of the column headers are correct and in the correct locations as per the example roster.
Make sure there is no excess formatting on the cells such as bold, italic, underline or hyperlinking.
Make sure the file type is a UTF-8 encoded CSV file or it will not be accepted.
Make sure the Course Information "Type" field on the course is set to "Course" otherwise you will not have the necessary permissions to upload that roster.