Welcome to the Roku Community and thanks for posting regarding the issue you are experiencing with finding the AV input on your Roku TV.
If you do not see the option for AV input when you go to Settings > TV inputs, can you provide us with a screenshot of what options you have available on that screen? Do you currently have anything plugged into the AV inputs on your Roku TV?
With more detailed information, we will be more than happy to continue assisting you. We look forward to hearing back your response.
Roku Community Moderator