There seems to be mis-information on this subject. Amp'd uses Verizon's network and roams wherever a Verizon phone can roam. I think the misconception is that Ampd's rich content like streaming TV and or data works on Verizons network only.

I have Ampd and I roam every single day on USCellular.. the phone works fine but I don't get data when I am roaming. And yes, the monthly bill from Ampd does not have any charges for roaming!