Barton, once considered the club's first baseman of the future, struggled greatly at season's start, batting .198 in 37 games before being optioned to Triple-A Sacramento on June 2, ultimately losing the starting job to the platoon of Brandon Moss and Chris Carter.
The 27-year-old Barton, who has one home run in 113 games with Oakland over the last two years, will face the tough task of battling that power-hitting duo -- which combined for 37 homers in 151 games this season -- for a job come spring.
Barton found his own power stroke during a 74-game stint with the River Cats, tallying eight home runs to go along with 35 RBIs and a .255 average. Upon his return to Oakland as a September callup, he went 2-for-7 in nine games.
Rosales, meanwhile, will also be in a battle for a roster spot this spring, and his is likely to come at shortstop, in the event the A's don't reel in a true everyday option by then. In the event they do, Rosales has an excellent shot of staying on board as a utility player, a role he's filled well since joining the A's in 2010.
Rosales, 29, hit .222 with two home runs and eight RBIs in 42 games over three stints with Oakland this year, starting 31 games at four different positions: 18 at second base, nine at shortstop, three at first base and one at third.