eduroam is not a replacement to your guest network, it is a complement to make your guest network and your community compatible with other eduroam participants.
Enabling eduroam on your campus provides four main features:
1) it allows your campus to welcome eduroam enabled visitors in a strongly authenticated way (the strong authentication also provides a way to authorize users to different resources)
2) it allows your own users to travel to eduroam enabled locations around the world (some places only have eduroam as a guest Wi-Fi)
3) it saves provisioning time to your institution and to the visitors since authentication is automatic and access is immediate
4) it improves security since your visitors use a standard protocol (WPA2-enterprise, 802.1X) that encrypts traffic between their devices and the Wi-Fi infrastructure