It's possible that this content required payment and any charges would have been shown to you on your screen before purchase. The Fury v Wilder fight is currently billed at $79.99 via ESPN+. You can view your recent purchases by going to http://my.roku.com and signing in there.
You can also put a PIN on your account as an added method of purchase protection. You can add a PIN by navigating to http://my.roku.com and finding Pin Preferences, then selecting the purple Update button.
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