Jackson was informed Sunday that he's made the Athletics' Opening Day roster, Scott Bordow of MLB.com reports.
Jackson made 25 relief appearances in the minors last year and posted a 2.57 ERA and 1.11 WHIP in 28 innings. Although the right-hander is unlikely to serve in a high-leverage role in Oakland's bullpen, he'll be rewarded with a major-league roster spot after recording a 1.80 ERA, 1.40 WHIP and 8:2 K:BB in five innings across five relief appearances this spring.