The deal was announced Friday.
Ross was 2-11 with a 6.50 ERA in five stays with the A's last season. The 25-year-old made 13 starts during his first four stints and later had five relief appearances in September with the AL West champions.
The 24-year-old Kirby-Jones hit .248 with 21 home runs and 69 RBIs at Class A Stockton.
Parrino, a 27-year-old switch-hitter, batted .207 with one home run and six RBIs in 55 games with San Diego.
The 25-year-old Werner went 2-3 with a 5.58 ERA in eight starts for the Padres.