There are a couple different ways to manage the Roku Channel Live TV Channel lists. You can use different Filtered Lists. As @DBDukes mentioned, you cannot remove any specific channel in the Live TV Guide, but you can "hide" them so they are not available to use while in LiveTV.
The main help section for the Live TV Guide is here. (https://support.roku.com/article/4420557730839)
The "Hide Channel" section is here. (https://support.roku.com/article/4420557730839#section-2)
Basically, when in the LiveTV guide, scroll all the way to the left (channel number) and press the * button on remote which will bring up "channel options". This is where you are able to hide and manage channels.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941