Sorry, I don't think I can help you with the specifics of your problem, but here's a dump of the settings I have for working eduroam in my "Internet connections":

Connection name: Eduroam
Connection type: WLAN
Network name (SSID): eduroam
Network is hidden: [ ]
Network mode: Infrastructure
Security method: WPA with EAP
EAP type: PEAP
Select certificate: None
EAP method: EAP MSCHAPv2
Username: (my username with domain)
Password: (my password)
Prompt password at every login: [ ]
Advanced/EAP
Use manual user name: [×]
Manual user name: (my username with domain)
Require client authentication: [ ]

The one problem with this setup I have is that the "use manual user name" bit is really needed for it to work, but it means that the N900 never automatically connects to Eduroam, you have to manually connect. And if you drop out of WLAN range or something, you'll get switched back to phone network until you again manually connect. It'd be cool if someone who understood EAP could eliminate this problem, is it a "feature" of the N900 implementation?

Edit: found out that the non-connectivity is Bug 3399