This was somewhat surprising, considering Roberts had been a key component of the 2011 squad that went from last place to first place. But Roberts' hitting fell off substantially this season, and the Diamondbacks have fallen off as well.
If anything, Bortnick's stock has fallen this season, so this is simply a case of the Diamondbacks getting something, however slight, instead of nothing.
It's not readily apparent why the Rays would be interested in Roberts. Evan Longoria's missed a lot of time, but is scheduled to begin a rehab assignment soon. Lately, Jeff Keppinger's been playing third base, and hitting with authority. Maybe the Rays are simply tired of waiting for utility infielder Sean Rodriguez to hit. If Roberts looks good, he can take over at third base with Keppinger shifting to utility chores. Until Longoria gets back, anyway.