I am surprised your 5 isp's do not offer ipv6. In my area the he two major ones in Albuquerque(CenturyLink & Comcast) both support ipv6 and I know of two local mom/pop isp's that support it too. But to be fair I also know of two local isp's that do not offer it. Roku should support it as they do not have a valid technical reason why they should not support the standard.
Still waiting for IPv6 support on Roku. FireTV supports IPv6, Chromecast supports IPv6, Apple TV supports IPv6, and yet Roku is the lone holdout, why?