I wanted to bump this thread, as I have been searching for the same thing for some time now. After scouring through the code for Cupcake, there is no option to force roaming anywhere within the code. The user above claiming to make it work is BS, as he has posted the exact same text on 5 other forums, offering no proof, only requesting people send him money.
Anywho, I am doing the same thing, posting
this info on various forums to get more hits to bump it up higher on the list. I have created an Enhancement Request on Google Code requesting such an option be integrated into the OS.
http://code.google.com/p/android/issues/detail?id=7603
I actually need some more people to "star" the request to bump it higher up on the list. If being able to force roaming is something you'd use even on a next-to-nothing basis, this is something you should look at and click the star.
Thx..