Look closely at the power brick. The text is likely very tiny. If it's labeled 110-220v, you're fine. But if it doesn't specifically list 220v, then it's not dual volt. Many power supplies like this are dual voltage, but don't depend on it without checking.
Dan Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
I am looking to upgrade my Roku to the Ultra, but I don't have it currently. This is why I am asking if the power pack is dual voltage, as I cannot look myself. Do you have this device? Are you able to see if the power pack is dual voltage?