[dongcarl]

Some roaming SIM cards aren't restricted by the Great Firewall, but in general, yes you'd need a VPN.

[cyberax]

ALL roaming SIMs aren't restricted unless the home telecom company cooperates. The roaming traffic passes over a global MPLS network to the home mobile network, so it's not restricted by the national firewalls.

[dongcarl]

TIL!