In cases of large events such as concerts, conferences, sports events, as well as natural disasters, quick and easy deployment of temporary WLAN systems on-site is very important. In general, deploying WLAN systems requires wiring the cables to the Access Points (APs) and/or switches, and configuring the APs and servers. Although Wireless Mesh Networking (WMN) technologies enable us to reduce the wiring cost, some additional configurations are still required when we deploy a secure user authentication mechanism (e.g. IEEE 802.1X) on WLAN systems. This paper proposes a quickly and easily deployable WMN system working on a secure WLAN roaming system operated by multiple institutions like in eduroam, the worldwide roaming system for research and education institutions. The APs in the system generate authentication paths automatically using Rad-Sec over the WMN to reduce the configuration costs of APs and authentication servers. The APs can perform user authentication and provide local services when they have lost the upper network temporarily or even when the authentication servers they are communicating with are down thanks to the local authentication technique using digital certificates.