The Rockies' usual catcher, Rosario not only was dealing with a right hamstring cramp on Tuesday night, but he revealed after the game that his left hamstring cramped on Monday night. Nonetheless, as designated hitter, Rosario managed to go 2-for-4. His 17th homer of the season, which barely cleared the right-field wall, broke a 2-2 tie.
"I thought it was a double, but when the umpire let me know, I was happy," Rosario said.
The Rockies also had solo home runs from Charlie Culberson -- the first of his career -- Charlie Blackmon and Todd Helton (his eighth of the season) in starting a 10-game road trip strong. The Rockies' last 10-game trip resulted in just one win, but they have won six of seven since.
The four-homer night came in the Rockies' first game at Camden Yards since 2007.
"They say this field is good for the hitters," Rosario said. "Now I know it's good."
The Rockies handed the Orioles, an American League East contender, their fourth straight loss.
"I think this is honestly something that we needed, kind of a kick in the pants to wake us up," Orioles outfielder Adam Jones said. "We're in a unique position, in back-to-back years trying to do something special. Last year, everybody said we couldn't. This year, we created the expectation."
Manager Walt Weiss didn't play Rosario on Wednesday at home against the Padres. But the Interleague game allowed him to use Rosario as the DH.
"Wilin, with his sore hamstrings, we were able to DH him and it worked out perfect," Weiss said. "He came through big, swung the bat really well tonight."
Rosario opened the fifth with a double to left that went deep enough for him to take extra care going into second base. When a Wei-Yin Chen pitch to Nolan Arenado bounced in front of the plate, Rosario hesitated then pushed to third just ahead of catcher Matt Wieters' throw. He scored on Arenado's single to cut the Orioles' lead to 2-1.
His homer off Chen (6-6), came after Michael Cuddyer walked to lead off the seventh.
"My legs are a little bit tired, but it's not hurting, no pain," said Rosario, who had both legs heavily wrapped.
Culberson's homer off Chen to lead off the sixth tied it.
Blackmon opened the eighth against Francisco Rodriguez with the 73rd home run, and 44th by a visiting player, hit onto Eutaw Street since Camden Yards opened in 1992. It was the seventh such homer this season.
"It's cool if you can do it," said Blackmon, whose homer was his third this season. "They'll put a plaque out there with your name on it. There are not a whole lot of plaques with my name on it going up anywhere."
Rodriguez left with a right groin strain after giving up a single to Dexter Fowler in the following at-bat.
Juan Nicasio (7-6) pitched through difficulties in the first and third innings and lasted six, giving up two runs on four hits and four walks. He struck out two.
The Orioles' Nate McLouth opened the bottom of the first with his eighth homer of the year and Manny Machado singled, but Nicasio fanned two of the next three hitters -- including MLB home run leader Chris Davis -- to escape.
With the bases loaded and one out in the third, Nicasio gave up an RBI single to Jones. But Nicasio got Nick Markakis to pop out to catcher Yorvit Torrealba, and ended the frame when Wieters lined into the glove of second baseman DJ LeMahieu.
"I concentrated on making a good pitch and keeping my fastball down in the zone," Nicasio said.
Said Orioles manager Buck Showalter, "One of the bigger plays of the game was the ball that Matty hit with the bases loaded and [runners] moving. We couldn't buy a break there."
Rockies relievers Josh Outman, Matt Belisle and Rex Brothers protected the lead, though Brothers gave up a solo shot to Wieters in the ninth.
Helton's solo shot to right broke a tie with Fred McGriff for 97th on the all-time hits list with 2,491. The homer was Helton's 362nd, one more than Hall of Famer Joe DiMaggio.