I currently have a satellite internet connection, that only offers a signal through wifi. I use YouTube TV to provide me with local and cable channels, but they do not offer a weather channel. I noticed that The Weather Channel is available in the Roku channel store, but when I try to add it, it provides me with a code to get the channel through my cable provider. Since YouTube does not offer the weather channel, can I still get The Weather Channel by uploading the code somewhere else?
The Weather Channel is listed under the "Watch with Cable" group in the Roku channel store. Unfortunately for you, that means your TV provider (YouTube TV in your case) has to have it in order for you to be able to authenticate it and get it to work.
While you cannot watch TWC with your current provider, I know there is at least one alternative (WeatherNation) that does not require authentication with a TV provider.
Find a friend that has one of the cable/satellite services that offer the Weather Channel in their cable package, and ask them to perform the validation for you to be able to watch the Weather Channel app on Roku. I had to to this when i switched from FiOS to YouTube TV.