Apparently NBC has blacked out the US Open on their roku app. Not sure why. Roku support has no clue.
Roku support has no clue because they have nothing to do with how NBC's channel/app works.
NBC want you to be watching via the NBC broadcast affiliate station in your area to protect the stations advertising revenue.
This is typical for most sports broadcasts. The contracts for carrying sports via streaming typically black out games/events that are available via local television - either by local over the air network affiliates, or on regional cable sports channels.
That's the problem. It is blacked out on my local NBC station. I had to sign on via the NBC app to see it. This happened yesterday and today. It did eventually come back on my local station later. I'm wondering if they blocked it.