Restricting Service Partner Data Use?

I'm heading into an are that does not have T-Mobile data and I'll be restricted to Service Partner data.  The restriction will be on AT&T and limited to 50MB.  My phone pulls updates and syncs all the time, the last time I entered the area I hit my data cap in less than 2 days (pictures and videos syncing to G+ and other activities that I don't normally do).  I may eventually limit what data is synced but as a general rule; if I disable Roaming on my phone, will that prevent my phone from contacting any data while on AT&T?

Thanks.