From sprint's website:
Sprint reserves the right, without notice, to limit throughput speeds, and to deny, terminate, modify, disconnect or suspend service if off-network usage in a month exceeds: (1) voice: 800 min. or a majority of minutes; or (2) data: 300 megabytes or a majority of kilobytes. Prohibited network use rules apply. See in-store materials or sprint.com/termsandconditions for specific prohibited uses.
These new terms and conditions will make it easier for customers to realize how much roaming usage they are permitted each month, as shown below:
* Voice Roaming - 800 minutes or a majority of minutes
* Data Roaming - 300 megabytes or a majority of kilobytes
Additionally, I found this, but am not sure if it is up to date:
Suspension of Data Roaming Service
* When customers reach their 300MB domestic roaming limit or $1,000 of international data roaming usage then their data roaming service is automatically suspended. This will help reduce unexpected overage charges for customers while controlling Sprint?s operational costs.
Suspension of Domestic Data Roaming Service
* Occurs automatically when the 300MB limit is reached and lasts until the first day of the next bill cycle.
* Redirects end user to a web page stating their monthly data roaming limit was reached.
o Customers on new plans (that charge a $0.25/MB domestic roaming overage rate) can:
+ Wait until the next bill cycle to continue roaming.
+ Choose to ?opt-in? to overage charges from the web page and continue roaming.
o Customers on plans that do not charge a $0.25/MB domestic roaming overage rate can:
+ Wait until the next bill cycle to continue roaming.
+ Contact Sprint to switch to the new plan that charges a $0.25/MB domestic roaming overage rate.
# Specialist must remove the Domestic Roaming Throttle (BDMTRM) SOC to un-suspend service after switching to the new plan.
* Does not apply to:
o On-network service
o Select CL Unlimited Plans.
So, I guess from my understanding is that despite the roaming charge warning we get, you won't be charged for roaming unless you opt to be after you reach your data limit.