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In Europe, a minimum number of services ("ports") must be made available at the hotspot. The list includes sending and receiving email (encrpytedly and unencryptedly), browsing web pages (encrpytedly and unencryptedly), and access to a wide variety of Virtual Private Networking (VPN) solutions which can connect you back to your home institution in privacy. The full list of ports is available in section 6.3.3 "Specifications and Operational Requirements: Service Providers" (p.31+) of the European eduroam Service Definition.
Apart from that, you should consider every eduroam network as a "normal ISP" network. In particular, the WPA2/AES encryption only protects your traffic while it is in the air; as soon as it travels onwards onto the internet, your traffic is not encrypted any more unless you chose to use encrypted transfer protocols (e.g. browse with https:// instead of http:// ; or if you started a VPN connection).
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