Rockies manager Walt Weiss was unhappy, too.
Weiss addressed the issue in a 15-minute meeting with his pitcher and catcher after the Rockies gave up 14 hits and lost 10-1.
De La Rosa lasted only 4 1-3 innings and allowed five runs in his first opening-day start. He drew jeers during the Marlins' five-run fifth when he stepped off the rubber several times, and he said he had trouble with Rosario's change in signals made with a runner at second base.
''He called a lot of my games last year,'' De La Rosa said. ''Today we probably were not on the same page. I still like him. That's all I can say.''
Weiss said the postgame meeting helped.
''There were some miscommunications,'' he said. ''We've got to get it straightened out.''
Jose Fernandez struck out nine and allowed one run in six innings, and Marlins newcomer Casey McGehee drove in four runs with two doubles. The sellout crowd of 37,116 was the largest for the attendance-challenged Marlins since their new ballpark opened two years ago.
The 21-year-old Fernandez earned the victory while becoming the youngest NL opening-day starter since Dwight Gooden in 1986, according to STATS. And he picked up where he left off last season, when he went 12-6 and was voted NL Rookie of the Year.
''I didn't know how I was going to react to opening day,'' he said. ''But it came out great.''
Carlos Gonzalez homered for the Rockies in the sixth.
''He's going to have a monster year,'' Weiss said.
But by the time Gonzalez connected, the Rockies trailed 6-0. Even he tipped his cap to Fernandez.
''When a guy like that is pitching, you expect that kind of game,'' Gonzalez said. ''He's one of the best.''
The Rockies, who began their first season since 1996 without retired first baseman Todd Helton, could have used his pop. His replacement, Justin Morneau, went 1 for 4. Michael Cuddyer, who won the NL batting title in 2013, went 2 for 4.
Fernandez's strikeout total matched Josh Beckett's team record for an opener. Fernandez threw 73 strikes and only 21 balls to 23 batters.
The crowd included Fernandez's grandmother Olga, who lives in Cuba. She saw him pitch for the first time since he left that country at age 15.
Her grandson improved to 10-0 in 16 career starts at Marlins Park with an ERA of 1.21.
''She told me, 'Good pitching. You've got to throw a lot more strikes, though,''' Fernandez said.
He threw plenty, given his improved run support. The Marlins, who finished last in the majors in most offensive categories last year, totaled 14 hits while scoring in double figures, something they did only four times in 2013.
Marcell Ozuna homered, doubled, singled and scored twice. Giancarlo Stanton had an RBI infield single and a run-scoring double. Adeiny Hechavarria singled three times and drove in a run.
NOTES: Marlins INF Rafael Furcal, who began the season on the DL with a strained left hamstring, said he expects to play five or six games on a rehabilitation assignment. He hopes to be activated around April 14. ... Weiss had two hits and two RBIs when he started at SS in the Marlins' first game 21 years ago. ... The Marlins' bid for back to back no-hitters ended with the second batter, when Cuddyer singled. Henderson Alvarez pitched a no-hitter for Miami on the final day of last season. ... Miami's Nathan Eovaldi is scheduled to start against Brett Anderson on Tuesday.