@cameronlhutton , If you view home>settings>system>system update, you'll probably see the last-updated date corresponds to when this problem began. The update has caused a variety of problems for people. Your post appears to have been merged in with 2-3 other threads on the same topic. Read through the prior posts.
Looking at past threads about various problems doesn't instill much hope that Roku will view this as a problem, or prioritize fixing it. I think your choices are:
1) Do a system>advanced>factory reset. During the initial setup, I think you can tell it you don't have internet access. It will install whatever version of software it came with. You could then use your tv as a "dumb tv" just to watch antenna tv. Never connect it to the internet.
2) If you want to stream, you could buy an external streaming box to use with #1 above.
Or, buy an inexpensive DTV tuner box with HDMI connector. Use that to watch antenna tv with your now-hobbled TV (until another update breaks you in some other way).
I'm using the MediaSonic HW-150 DTV tuner. It's not bad, except for the channel management (setting hidden and fav'ed channels). Once it's setup, it's not too bad to use. It would definitely be an improvement over *no* antenna tv.
I also have a ViewTV AT-300, and an iView 3500. I'm going to switch to one of them today, and see how it compares. (Then I'll switch again, to be able to compare all three. There's others on Amazon. These three get the best reviews/"best of" pages. But, there could be something better on Amazon that hasn't been recognized yet.
Anyway, even if your antenna tv worked without internet, the update was a step backwards in other ways. If you liked favorites, that's gone. If you liked holding up/down button to continuously change channels, that doesn't work anymore. Roku added 1000+ streaming channels to Antenna TV. You can imagine how nice that is to scroll through one channel at a time, over and over, for the rest of your life. (You can hide-all in settings>Tv Inputs. But, you can't hide some. Also, you can left-arrow to guide, and the up/down arrow work faster there. Plus the << & >> keys scroll by page. That makes it better.).
"People are often amazed at how much we’ve done with the number of engineers we’ve got." (Roku CEO Anthony Wood, Austin Statesman, Oct 4, 2019). "Amazed" is one way of putting it.