You would need to setup a VPN (Virtual Private Network) to encrypt your Roku from your ISP. And you would need to run a local DNS server as your ISP is providing the name to IP mapping.
Why would you ? Why would your ISP care if you have a Roku ? Your ISP would see the small amount of encrypted data through your account for one HD Stream and would not care anyway.
But really the above is certainly not your issue. Your issue is a poor local network or internet speed, an ISP issue or you just need a larger ISP bandwidth plan.
TheTick (aka "Moose Twit" affectionately called by chht)
Roku 3 for Pokémon TV / YouTube / Animal Planet GO / HBO GO. Chromecast for most other media because Roku Mirroring sucks , how many clicks in Wndows 10 (about a dozen) to Miracast on Roku vs 2 with Chromecast.
Verizon FIOS TV and Internet Service