The result dropped the Dodgers into second in the National League West and kept the Rockies 1 1/2 games behind the first-place D-backs.
For Iannetta, the homestand was an exercise in bad luck. In Wednesday's 4-3 loss to the Pirates, Iannetta was robbed of a possible game-tying single by a diving Adam Frazier. In Friday's opener against the Dodgers, his seventh-inning homer gave the Rockies a 5-3 lead, but some hoary relief pitching led to an 8-5 loss.
"We just want to collect as many wins as possible -- it doesn't matter who it's against," Iannetta said. "We played a phenomenal team in the Dodgers."
With Sunday on the line, Iannetta showed the plate discipline that he foreshadowed at the start of the homestand, when he said he felt past his season-long timing issues. Manager Bud Black admitted thinking of going to left-handed-hitting Carlos Gonzalez, but decided to stick with his catcher.
"It was a decision, but we felt good about Chris, and Chris's ability to be selective and get a good pitch to hit," Rockies manager Bud Black said. "He fouled a pitch off. The first pitch looked to be a hanging slider. From there, the kid missed outside of the strike zone.
"That situation, bases loaded, bottom of the ninth, it makes it tough on the pitcher."
DJ LeMahieu opened the ninth with a single to right field off Floro, and took second on Yasiel Puig's bobble. A one-out intentional walk to David Dahl and a two-out intentional pass to Ryan McMahon -- whose homers won the games on Friday and Saturday -- set up Iannetta.
"I was smiling," said Iannetta, who stormed away unhappily after plate umpire Sean Barber called a looking third strike in the seventh, but finished the day happy. "I wanted it. I wanted that at-bat."
With Dodgers All-Star closer Kenley Jansen out with an irregular heartbeat, the Dodgers lost the last two games in the ninth. On Saturday, JT Chargois gave up McMahon's three-run homer with the Dodgers leading, 3-0.
The Rockies finished a stretch of 17 straight days of games -- all against either prime contenders or above-.500 teams with hope -- 9-8. For much of it, the offense and bullpen struggled.
But in winning the final three games against the Dodgers, the Rockies began to move past some of the problems. Closer Wade Davis (2-6), who gave up two home runs while losing Thursday's series opener, overcame a two-out walk for a scoreless top of the ninth. It finished a performance that saw the bullpen give up just one run in the final three contests.
"We've had some things not working at the same time that whole time," said Davis, who suffered blown saves at St. Louis and Milwaukee before Thursday's struggle. "Definitely to come out on top is good."
After giving up nine runs in 4 2/3 innings on Monday -- his first start after missing five weeks with a right middle finger blister -- Chad Bettis limited the Dodgers to one run on three hits in 6 1/3 innings, with four walks and three strikeouts.
"Really, it was just getting back to executing," Bettis said. "I felt like I got away from that a little bit last start. It wasn't anything major that I needed to work on, just minor adjustments that I've already done."
While Bettis had the lead much of his time on the mound, Rich Hill was almost as effective, going six innings and giving up three runs (two earned) on four hits.
The Rockies benefited from Chris Taylor dropping a pop-up and Yasmani Grandal missing a pitch for a passed ball to set up Trevor Story's sacrifice fly in the first inning. DJ LeMahieu doubled to lead off the fourth and scored on David Dahl's single.
Charlie Blackmon's leadoff homer in the sixth -- his 22nd homer of the season -- gave Bettis a 3-0 lead.
Rockies manager Bud Black went to lefty Jake McGee for a left-on-left with Max Muncy, and was rewarded with a strikeout. Dodgers manager Dave Roberts played a favorable matchup when Justin Turner lashed a double to the right-field corner. Scott Oberg gave up Brian Dozier's two-run single but struck out Manny Machado.
Black went to Adam Ottavino to start the eighth. Puig singled to left to improve to 6-for-11 against Ottavino, and Cody Bellinger singled hard off the right-field wall. Matt Kemp tied it with a sacrifice fly, and Ottavino allowed no further scoring.
ONE WAY OR ANOTHER, ARENADO PLANS TO PLAY All-Star third baseman Nolan Arenado missed his second straight start after leaving Friday night's game before the fifth inning with right shoulder soreness. However, he almost made Sunday's start and plans to be in the lineup -- either as third baseman or designated hitter -- Tuesday at Houston.
Arenado grounded out as a pinch-hitter in the eighth. Throwing has been the issue for him. Arenado tested the arm before the game and said the harder, longer throws were not a problem.
"It hurt when I tried to baby it, but when I really let it go it wasn't that bad," Arenado said.
SOUND SMART Sunday was the second time this season the Rockies won with a game-ending walk. The first one was drawn by Tony Wolters on April 7 against the Braves. Also, the Rockies have won two straight games in walk-off fashion for the first time since May 18-20, 2014 -- Justin Morneau's homer against the Padres and Arenado's two-run double against the Giants.
UP NEXT The Rockies and defending World Series champion Astros split two games at Coors July 24-25, and Tuesday starts a two-game set at Houston's Minute Maid Park -- Rockies righty German Marquez (9-9, 4.69 ERA) vs. righty Justin Verlander (11-7, 2.50) at 6:10 p.m. MT. Marquez's 3.09 road ERA is ninth among qualified National League pitchers. He held Milwaukee to three hits and two runs in seven innings in his last road start.