Domestic roaming is included, BUT when roaming you are using your anytime minutes so if you go over you will incur overage charges. Also too much roaming can/will get you terminated.
Off-network Roaming: The primary use of your Device must be for domestic purposes within the Sprint-owned network. Domestic means use in the 50 United States and U.S. Territories (except Guam). Sprint reserves the right, without notice, 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. The display on your device may not always be on and will not indicate whether you will incur roaming charges. You can monitor usage online through My Account. Roaming is not available with single-band phones, or to customers who reside or whose primary use is outside an area covered by the Nationwide Sprint Network. Sprint may limit or terminate service if you move outside of the Sprint owned-network.
Domestic roaming in roaming within the United States. Domestic roaming is included in on Simply Everything and Everything Data plans. You are essentially using our roaming partners network when the Sprint network is not available.