This happened despite using the ATT modem/router. I can check security, but he had third party AV, URL checker and a firewall up, he is older and basically just plays games on it, pays bills, etc. No browsing to shady sites.
Edit: To all of you who dislike my posts on this topic, please bear in mind the error message and phone number appeared on the Roku TV, not when I went to a Roku site. It also happened using only the ATT ISP modem-router. Clearly this TV was hacked or altered or re-sold after being returned. Regardless it makes for a poor customer experience and others have had the same error message on the Roku TV, not when trying to go to Roku’s site. If this had happened on an AppleTV, what would you be saying then?