Per A's Press Release:
To clear spots on the 40-man roster, the A’s outrighted right-handed pitcher Andrew Carignan to Sacramento and designated right-handed pitcher Jim Miller and infielder Brandon Hicks for assignment.
I'm surprised they designated Miller -- who had some nice moments at the back of the bullpen -- and held onto Jesse Chavez and Jermaine Mitchell. It would seem that Rosales remains in the A's plans with the DFA of Hicks, although I expect that might change if Hicks isn't traded/claimed.
The roster additions all make sense, but BWH indicated the other day that Simmons is also eligible for the Rule-5 draft, which seems like quite an oversight. Susan Slusser confirms that Simmons is eligible, and cites him as the most likely A's player to be snatched away.
Update: Here's Jane Lee's article on the same topic.