I found a short description on how to disable data roaming on Android 4.2 On my Fairphone 1, I do not find the option described. How do I disable data roaming, then?
First go to settings
Then open the phone menu (here Sim-Verwaltung in german)
Then go to the section Roaming
If you want data roaming you have to go to the sub menu, normaly data roaming is not selected