Can you provide some clarification? Root passwords are not carried over in a snapshot for security purposes so each time you create a droplet from a snapshot (and not using an ssh-key) a new password is generated and emailed to the email address on the account.
This temporary password can only be used via the console or SSH in order to log in at which point you must create a new password to replace the temporary one. The process goes a bit like this:
Make ssh connection
Enter username root
Enter temporary password
Re-type temporary password to start the password change process
Type new password
re-type new password
If you attempt to connect to SFTP instead of SSH or the console you will not be able to until this password change has been completed which might look similar to a failed login due to the password but is caused by the prompt to change the password before any other activity can be done.