You’re probably correct. Your hospital is probably running an advertising campaign through roku and wants to track how successful it is, and exclude serving ads to existing patients (customers).

You can opt out here (ctrl f “ad personalization”): https://docs.roku.com/published/userprivacypolicy/en/US#:~:t....

Or global opt out (do this on all of your devices): https://optout.aboutads.info/?c=2&lang=EN