Thanks for reaching out to the Roku Community.
To provide further assistance, could you please provide us with more information? Specifically, we would like to know if you are still able to access the sleep timer feature on your device after adding the Roku Streambar Pro. Additionally, we would appreciate it if you could try setting a sleep timer using the following four methods: from the Settings menu, Shortcut tile, Options menu, and Voice command. This will help us diagnose and resolve any potential issues.
Please follow the steps here: How to use a sleep timer to turn off your Roku TV
Keep us posted on what you find out.