Third baseman Chase Headley went 1-for-3 for the Padres (3-4). San Diego shortstop Everth Cabrera had two hits and scored twice.
The Padres scored first, as Jesus Guzman had an RBI single in the first inning.
Jordan Pacheco had two hits and knocked in two runs for the Rockies (3-2), one coming on a double off Weber in the fourth inning.
San Diego pitcher Sean O'Sullivan, making his second start of the spring, allowed one run on two hits with two walks in three innings. He ran into a little bad luck when a potential double-play ground ball hit the foot of an umpire, resulting in an infield single for Rosario.
"He settled down," Padres bench coach Rick Renteria said of O'Sullivan. "He kept his fastball down. He got into a little trouble with his breaking ball."
O'Sullivan, a non-roster invitee, has allowed one run in five innings this spring. Luke Gregerson, one of the best late-inning relievers in the National League, tossed a scoreless seventh inning.
Colorado pitcher Tyler Chatwood -- a candidate for the fifth starter job -- allowed two runs on five hits with one walk and two strikeouts.
"I felt good," Chatwood said. "I felt like I commanded the zone really well. I could have finished off some guys in 0-2 counts a little earlier. Threw a little too many pitches there, but overall I felt good about it."
Drew Pomeranz followed Chatwood and allowed one unearned run over two innings.
The Padres' other squad dropped an 11-6 contest to the A's in Phoenix with Bud Black at the helm. The game in Peoria was managed by Padres bench coach Rick Renteria, who next week will skipper Team Mexico during the World Baseball Classic.
Up next: Veteran Jason Marquis -- who returned on a one-year, $3 million deal in December -- gets his first start of the spring when the Padres host the Royals at 12:05 p.m. PT on Thursday in Peoria. Marquis won six games last season after signing with the team following his release from the Twins. He'll go two innings. Newcomers Tyson Ross and Wilfredo Boscan are scheduled to go two to three innings. Ross impressed the Padres with his big arm in his spring debut on Saturday, hitting 96 mph with his fastball, though he allowed a two-run homer to Jason Bay and took the loss against Seattle.