Unless Google and Roku have reached a very recent agreement on renewing the YouTubeTV app carriage agreement, new YouTubeTV installations can't be added to Roku accounts. Supposedly if it's already present in the Roku account it should install to any Roku linked to that account.
If by "available" you mean it is present on the channel grid on the Roku home screen that would indicate YouTubeTV is present on this account. Try this on your Premiere: Settings > System > System update > Check now.
Remember, new channels are added to the bottom of the grid.
After that, if you have it on one Roku but not the other, are they both linked to the same Roku account (same email address on both via Settings > System > About)?
Meanwhile YouTubeTV can be accessed from the left side menu on the standard YouTube channel app.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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