It has been my observation that you should not include...

Change AllowRoaming to 0 (not sure if this is needed or not)
If this is a true indicator, then 0 = *off and 1 = *on

I was unable to get a data connection while roaming with AllowRoaming = 0, however when I switched it back to 1 everything worked perfectly.

If someone were to make a .CAB, they should use the following parameters...

HKEY_LOCAL_MACHINE\Software\OEM\PhoneSetting\Netwo rkService
- Change ItemCount
- DWORD Data = 3
- Create a new String
- Name = ItemName3
- String = Roam Only
- Create a new DWord
- Name = ItemValue3
- DWORD Data = 3

HKEY_LOCAL_MACHINE\SOFTWARE\OEM\InitProv\PhoneSett ing
- Change ItemCount
- DWORD Data = 3
- Create a new String
- Name = ItemName3
- String = Roaming
- Create a new DWord
- Name = ItemValue3
- DWORD Data = 3

As a note, I found that ItemValue3 can have DWORD Data = 2 or 3, and will still force roaming and data roaming. I'm not sure what the difference is, if someone knows, I would love to hear it.

Thanks,
Zak