said by TBBroadband:
VM and Boost were designed not to have roaming. Sprint MVNOs are now given that option but costs them extra. I have a Straight Talk phone on the Sprint network and it will roam onto VZW when needed. If you also read the newer Sprint contracts roaming is not fully unlimited and is a "bucket" of usage.
AND it tops out at 256 kbps. Some "unlimited" plan.