First-base umpire Hal Gibson initially ruled Panik safe, but after a review, the call was overturned to end the game.
"I thought he was definitely out, but with replay, you can't see everything clearly, you don't make the call," Roenicke said. "They got the call right. He was out. But you couldn't see, in slow motion, his foot touching the bag when the ball was in the glove, but you could see in one of the angles that he was out."
Had the "safe" call on Panik remained intact, the Giants would have had runners on first and second base with Brandon Belt due up.
"I just don't see how it got overturned. It was so close," Giants manager Bruce Bochy said. "... But they did, and that's the game."
Bochy believed that none of the multiple replay angles definitely proved Panik was out. "You always hear that word 'conclusive,'" Bochy said.
It marked the second time this year that an overturned call concluded a Giants defeat. On May 6 at Pittsburgh, umpires overturned an initial "out" ruling when Buster Posey tagged Starling Marte at home plate.
The Brewers' replay came after the Giants had successfully challenged a third-inning call, resulting in an infield hit for Pence.
Facing Brewers right-hander Jimmy Nelson with two outs, Pence hit a grounder up the middle that shortstop Jean Segura managed to grab. Segura whirled in a 360-degree motion and made a one-hop throw to first base, prompting an out call from umpire Hal Gibson.
The call was overturned when a video review showed that Pence's foot hit the bag at about the same time Segura's throw hit the dirt.
Caitlin Swieca is an associate reporter for MLB.com. Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.