You do need a roku device at each tv, but roku doesn't charge a fee. And apps like netflix and prime don't charge by device either, you sign in at each device with same credentials. There might be limit of how many devices aparticular app can run at the same time on different roku's, but you won't be charged, it was just get an error message. I pay netflix $16 a month for upto 4 devices run at the same time, and 4k.
Edmund Roku Community Streaming Expert
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