I would never rely on these free roaming deals unless I get it in writing that I will not be charged. I don't want to come back and be presented with a $10,000 bill because of some misunderstanding or fine print.

Easier just to get a local SIM, they are cheap.

Here is a question about Project FI, it says $10/gb internationally but is that per country and per billing period? Say during the billing period I visited Thailand, Indonesia and Singalore and used data there and collectively did not exceed 1gb, is it $30 or just $10?