Free Wireless LAN services, also known as 'Free Wi-Fi,' have long been widely deployed all over the world for attracting tourists as well as shoppers. Most of the Free Wi-Fi today are based on the combination of open Wi-Fi and Captive Portal, and have a lot of security problems such as eavesdropping and Man-in-the-Middle attacks. Next Generation Hotspot (NGH), based on the Hotspot 2.0 specification, has been developed as a new conceptual standard that brings higher security and usability to Public/Free Wireless LAN services. Although some operators have already introduced NGH, world-wide roaming system for Free Wi-Fi is still in a nearly stage of development. We have developed an NGH testbed system and started 'Cityroam' which is a pilot service of secured Free Wi-Fi with international roaming capabilities. Cityroam aims at connecting as many roaming systems as possible and also integrating eduroam the roaming system for research and education institutions. This paper presents the architecture overview of Cityroam and, in particular, its trust and service designs. The effectiveness of the system has been confirmed through the pilot service and the City Wi-Fi Roaming trial involving a lot of telecom and Wi-Fi operators.