Re: Roaming is completely knackered.
I'm pretty sure that mobile internet is always routed through your home network.
And I know that when your phone first sets up a roaming connection with a local network, there is a check with your home network to see that you are kosher.
So both these would be knackered by an outage at home.
Not sure about calls when you're roaming. Is there some sort of contact every time - eg to see that you have credit or to bill you?