First, Jeff Beliveau, who was designated for assignment earlier this week, was claimed by the Texas Rangers. Though this is a minor move, I suspect the Cubs might be looking for a Beliveau-type by the end of spring training. They could use more lefties in the bullpen.
Second, Gerardo Concepcion, the Cuban teenager signed to a $7 million deal last year, cleared waivers and was sent outright to the Kane County roster. It's possible that signing is a complete bust; there's been some speculation here that Concepcion was signed simply as a come-on to get Jorge Soler to sign. That might be true; at this point, it appears they could be teammates at Kane County in 2013 (at least until Soler likely gets promoted to Daytona).
Honestly, I'm not sure why teams do this. What's the point of claiming someone you have no intention of putting on your roster? Rosario had been in the Marlins organization, and pitched briefly (and not very well) for them in 2010, 2011 and 2012.
Anyway, he's gone. Nate Schierholtz, whose signing was reported last week, has officially been signed, via press release from the Cubs. These moves leave the 40-man roster at 39, so they'll still have to move one more player to make room for both Jackson and Villanueva.