If you no longer have your Roost battery(ies), and are not monitoring anyone else's battery(ies), you may want to delete your Roost account. You will continue to receive automated emails on any batteries in your account unless you delete your battery(ies) or delete your Roost account.
To delete your Roost account, open the Roost app. Tap the setting icon in the upper left-hand corner of the home screen. Tap "Delete Account."