can roku I buy here and used in China for my relatives?
Does chinese higher voltage a problem?
It does not look like any of the ROKU devices officialy support anything over 110v, so you may need to get a new power supply or a step down transformer for it. On some user forums I did see some people say they had tried it on 220 and it worked.
Also, to connect to streaming services outside of china you would likely need to set up a VPN on your router since most subscription services require you to be in the USA.