Update 2017-11-13: Now you need to use ca-cert=/etc/ssl/certs/QuoVadis_Root_CA_2_G3.pem. I suppose they changed the certificate.

Here's a NetworkManager connection for Eduroam. This can live under /etc/NetworkManager/system-connections. Fill in your MAC address, your username and password, plus a unique UUID.

[connection]
id=eduroam
uuid=3ef39a8f-3020-4cf3-8e07-382719a4e6f9
type=wifi
permissions=

[wifi]
mac-address=10:02:B5:ED:5D:EB
mac-address-blacklist=
mode=infrastructure
ssid=eduroam

[wifi-security]
auth-alg=open
key-mgmt=wpa-eap

[802-1x]
ca-cert=/etc/ssl/certs/AddTrust_External_Root.pem
eap=peap;
identity=db57@sussex.ac.uk
password=YOUR_PASSWORD_GOES_HERE
phase2-auth=mschapv2

[ipv4]
dns-search=
method=auto

[ipv6]
addr-gen-mode=stable-privacy
dns-search=
method=auto