Alex Claudio and Jon Edwards have been optioned to AAA Round Rock, according to the beat writers on Twitter.
In addition, although an official move has not been made yet, Sam Freeman, acquired from St. Louis earlier this spring, will not make the final 25 man roster, according to the beat guys. Freeman will presumably be designated for assignment, and either traded or put on waivers. If he clears waivers, he'll be able to be outrighted to the minors.
Jon Daniels had previously said that Freeman was expected to make the club, but he pitched poorly after coming to Texas, and in particular, struggled against lefties.
Anthony Bass and Phil Klein are both going to Oakland with the team, and would presumably get the final two spots in the bullpen (the open one and the one that was going to be Freeman's), although the Rangers are apparently still talking to teams about acquiring a relief pitcher.
In addition, lefthanded reliever Andy Oliver, who had a decent camp for the Phillies, rejected an outright assignment and became a free agent today. Oliver is someone the Rangers could opt to look at as a lefthander in the bullpen.
As things stand now, though, the bullpen will be entirely righthanded.
UPDATE -- Per Jon Daniels, Anthony Bass is the guy on the bubble right now:
#Rangers GM Jon Daniels: "Anthony Bass will travel to Oakland & unless there's a late acquisition he'd open up in the bullpen."— Stefan Stevenson (@StevensonFWST) April 4, 2015