Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
If you have a paid subscription to CBS All Access through Optimum, then in all probability you will only be able to view it via Optimum.
That's why I prefer to subscribe to such 3rd party channels directly on the channel's website. Then I can view it any way they make available, browser on computer, app for mobile device, app for streaming device.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T