Sashio
Currently, there is no channel yet that you can just install and watch LindellTV on your Roku.
You can watch LindellTV on your Roku (and all other web content), by navigating to https://lindelltv.com/ on your phone or laptop and then casting it to your TV, or using an HDMI cable.
With my laptops, I generally use an HDMI cable for streaming directly to the TV. With my Android phones, I use some free apps from the Play Store that allow me to cast web content to the Roku. I generally use Web Video Caster, but other good ones are "Video and TV Cast for Roku" and Castify/Rokify.
There are other ways to screen mirror or use Airplay for IoS/Apple devices, but I am unfamiliar with the exact method for this. More info on that can be found here https://support.roku.com/article/360057488733