A warm welcome here in the Roku Community, @Mocapmat!
Currently, the Sleep timer feature is only available on Roku TV.
No worries! We'll take note of your suggestions as your satisfaction and convenience are what we aim for.
Please don't hesitate to let us know if there's anything you'd want us to address and we'd be more than willing to listen.
Best regards,
Carly
Carly Y.
Roku Community Moderator