Welcome to Roku Community.
The current features offered, do not allow for the blocking or deleting of specific channels within the Live TV section. However, we would like to inform you that you can hide the channels from the menu by using the "hide" feature. This feature will hide the channel from being displayed when scrolling through, but it will not remove it entirely from the system.
To learn more on this matter, please visit the following link which details the process of modifying the Live TV Channel Guide to only display "over-the-air" TV listings: How to find TV listings using Live TV Channel Guide.
Hope this helps. If there is anything else we can assist with, please do not hesitate to reach out.