No, it's not interested in that spectrum.
600/800/1900/2500 will be enough for the foreseeable future.
Roaming? Sprint is gonna buy some spectrum, new bands in its handsets, replace the panels AGAIN just so the 1% or whatever of its subs who roam internationally can have LTE on AWS?
HSPA+ is plenty fast enough for roaming with only 4 bands longterm, much easier to support. Iphone already includes it even on CDMA versions and if sprint wants all its smartphones to have roaming, it'll mandate HSPA+.
Get into the AWS game? Why do people think Sprint NEEDS to have a band just because "everyone else has it"?