Grandal was the star for the second straight night as he continues his impressive start.
"I don't want to imagine where we would be without him behind the plate and at the plate with what he has done: Getting big hits for us, getting on base, driving runs in and catching 12 innings tonight,'' Roberts said. "He has done amazing things."
Scott Alexander (1-0) pitched the 11th inning for the win while Webb (0-1), who was called up earlier on Tuesday, got the loss.
Alex Wood didn't figure into the decision, but he was solid. He allowed an unearned run and two hits over 5 2/3 innings. This came in the wake of his last outing, when he gave up more runs than in any game since July.
"I felt really good tonight,'' Wood said. "It was just my stuff. My fastball command was good. I was behind it and I was commanding it really well and it was sinking tonight.''
Unfortunately, that sinking feeling wasn't restricted to Wood's offerings. While the Dodgers close in on a possible sweep, the win left a bitter taste in one corner of the somber clubhouse.
Jansen is the Dodgers' closer, but another unsettling ninth inning raised further alarms for him.
"When you have a two-run lead and you have the best closer coming into the game, you don't expect to use three other relievers,'' Roberts said. "We have to get Kenley right because we are going to need him to accomplish what we want to accomplish.''
The Dodgers turned the game over to Jansen, ahead 3-1. But Eric Hosmer opened the inning with a homer off the struggling two-time All-Star and Chase Headley, as a pinch-hitter, tied the score with a sharp double to right, which scored Franchy Cordero.
"Today, I missed location and I missed by a lot,'' Jansen said. "I just have to find it and be consistent and I will be fine. But to Eric Hosmer, that ball was down the middle -- he got me.''
It was Jansen's second blown save in four appearances, after having just one in 42 chances last year. Jansen was lucky not to get tagged with the loss as he was aided by Chris Taylor's sensational catch. Taylor jumped near the top of the center-field fence to rob Christian Villanueva of extra bases.
"Villanueva, again, down the middle -- that's not me,'' Jansen said. "Headley, he put a good swing on it and he got me on that one. But most of them were because of my location.''
Matt Kemp had three RBIs as he continues to torment his former team. He has six RBIs in the series' first two games and his first-inning homer, a two-run blast, was his second in as many evenings. Kemp's three home runs ties him for the club lead.
If not for Jansen's hiccup, the clubhouse would have been thumping with loud music afterward. Instead it was quiet, as players hustled out into a night that lasted longer than most would have imagined.
"I have confidence in myself that I will find it, it's just a matter of time,'' Jansen said. "Hopefully I can get an opportunity tomorrow because tonight, that's no who I am.''
MOMENTS THAT MATTERED Bellinger had his biggest impact by husting down the line. When he hit a sharp one-out grounder to second with two men on in the 12th, it looked like the Dodgers' game-turning rally was circling the drain. But Bellinger, who's among the fastest Dodgers, beat Freddy Galvis' relay to first after Enrique Hernandez was erased at second. If Bellinger doesn't go hard to first, the inning would have been over, instead of the Dodgers putting the go-ahead four runs on the scoreboard.
SOUND SMART It's easy to tell the veterans from the rookies. When a foul ball found its way to the Dodgers' dugout steps, Chase Utley made a sweet snag. He predictably flipped the ball over his head into the stands, and it quickly came right back. Utley, in his 16th season, forgot about the extended netting which now protects fans in Major League parks.
HE SAID IT "It boils down to he is not executing like he normally does. I can't speak to if it is mechanic, all I can tell you is what I see with my eyes. And [his cut fastball] is not doing what it used to do." -- Roberts, on Jansen's struggles
UP NEXT Dodgers right-hander Kenta Maeda (1-1) will draw Luis Perdomo (1-1) in Wednesday's series finale, with first pitch at 7:10 p.m.
Maeda hopes to get on track after a scratchy outing on Friday when losing to the Diamondbacks. He recorded but eight outs in allowing two runs on five hits with two walks. Against the Padres, Maeda is 3-3 lifetime in eight starts, with a 4.50 ERA.
Max Muncy, who was summoned from Triple-A Oklahoma City on Tuesday, is expected to make his first Dodgers start at third base.
Jay Paris is a contributor to MLB.com based in San Diego.