The homer was Jones' 17th of the season and his second career walk-off. The first came on May 24, 2011, against Kansas City.
Jones underwent an MRI on both hands and wrists during Monday's off-day that revealed nothing more than contusions, but Jones had managed only a single hit in the five games since before his ninth-inning single ended an 0-for-18 slide.
"I'm fine," Jones said when asked about the injury. "It's frustrating that I wasn't swinging the bat as well. There's no excuses coming out of my mouth."
Rosenberg was a total unknown to Jones, as the 26-year-old righty was making his Major League debut.
With that in mind, Jones' plan for the at-bat was a simple one: Look for a pitch to drive.
After taking a 94-mph fastball for strike one, Jones found what he was looking for.
"I put a good swing on a good pitch," Jones said. "It just went out of the park."
"It just kind of hung up there," said Rosenberg of the final pitch.
The blast tied Jones for third in the Majors with 17. Eleven of those have either tied games or given the Orioles a lead.
The win brings Baltimore to 8-2 in extra-inning games, including eight consecutive wins. Of those eight, Saturday starter Tommy Hunter has been on the hill for three, and in each, Jones has provided the game-winning homer.
"I don't know if that's the charm or something else," Hunter said. "You like the game to end with a 'W' on the wall and it did, but next time, let's put it next to my name instead of that no-decision again."
Hunter, who wasn't officially added to the roster until three hours prior to game time, allowed three runs in seven innings. All three runs came from solo shots on pitches that Hunter missed with up in the zone, a recurring problem for him this season.
The three bombs -- by Jimmy Rollins in the third, Jim Thome in the fourth and Hector Luna in the fifth -- boosted Hunter's homers per nine innings mark to a Major League-worst 2.22.
While the Phillies were able to muster eight hits, Hunter finished with zero walks and managed to escape damage by inducing 10 ground-ball outs, including a pair of double plays. The Orioles turned four double plays on Saturday, a season high.
Aside from the solo home runs, Hunter attacked the zone en route to an economical performance, finishing with only 86 pitches.
The key to Hunter's success was going right after hitters, as he threw 59 of his 86 pitches for strikes, including 18 of 27 first pitches.
Baltimore's offense, reliant on the long ball for so much of the season and in the 12th inning on Saturday, managed four runs without an extra-base hit in the first 11 innings, thanks to a little help from Philadelphia's defense.
In the third, Robert Andino and Endy Chavez both singled before moving over on a warning-track flyout by J.J. Hardy. Davis' RBI groundout brought Andino home and tied the game at 1.
The Orioles scored two to grab a 3-2 lead in the fourth. After Nick Johnson reached on an error by Rollins, Wilson Betemit hit a slow grounder that Philadelphia starter Vance Worley fielded and threw to second in plenty of time to beat Johnson. However, second-base umpire Fieldin Culbreth ruled that Rollins was off the bag.
Phillies manager Charlie Manuel came out to argue but to no avail, and Ryan Flaherty followed with an RBI single. Later in the inning, Betemit scored when Chavez reached on an error by second baseman Mike Fontenot.
Worley, pitching his second game since coming off the disabled list because of right elbow inflammation and a bone chip, finished allowing three runs -- one earned -- in six innings.
In the seventh, the Orioles grabbed a 4-3 lead against Jake Diekman as Hardy walked, Davis singled on a blooper that went off the glove of Fontenot in shallow right and Matt Wieters hit an RBI single up the middle.
But the Phillies answered right back in the eighth against Pedro Strop, scoring when Juan Pierre, Hunter Pence and Thome hit consecutive one-out singles to tie the game at 4.
With the bases loaded and one out, Strop got Ty Wigginton to hit a grounder sharply to Hardy, who deftly handled an awkward bounce off the lip of the grass to start a double play and preserve the tie.
"You will not see a better play by a shortstop than J.J. made on the double play," manager Buck Showalter said. "The ball hit the lip and went straight down. You just don't make those plays."
"It's just a reaction thing," Hardy said of playing the awkward bounce, the first of its kind he's faced in Baltimore. "You're never expecting it."
The Orioles' defense made three outstanding plays in extras. Steve Pearce, who entered as a pinch-hitter in the eighth inning, made a sliding catch in the 11th and followed with a diving grab in the 12th.
Andino also came through with his glove, leaping to snatch a line drive that was scorched off the bat of Rollins in the 12th.
"If we don't do some of those things defensively," Showalter said, "we're not sitting here with a 'W.'"