Will Rhymes drove in the lone run for the Tigers, who arrived after dropping two of three at Yankee Stadium. Detroit doesn't begin the home portion of its schedule until Friday.
Arrieta (1-0) allowed one run and six hits in six innings while working against a lineup operating at less than peak efficiency.
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"We just didn't do much offensively," manager Jim Leyland said. "Without making an alibi, we had two or three guys throwing up during the game, sick. ... I certainly don't want to downplay the fact their guy pitched good. I don't mean that. It was just a little rough for some of the guys."
Including slugger Miguel Cabrera, who went 0 for 4. Detroit's cleanup hitter stranded a runner at second in the first inning, left runners at second and third in the third, flied out with a man on in the fifth and grounded out leading off the eighth.
"I have no excuse. I am going to play and do my best," said Cabrera, adding that he vomited twice while at the ballpark.
"He was sick as a dog," Leyland noted.
With the score tied at 1 in the fifth, Felix Pie walked and went to third on a double by J.J. Hardy before Roberts hit a 1-2 pitch from Rick Porcello (0-1) over the wall in right-center. Roberts has Baltimore's only two home runs this season and has a team-high eight RBI.
"Roberts hit a big home run down in Tampa and he hit another one today," Leyland said.
Detroit pitchers have yielded 10 homers in 33 innings this season.
"That's been our nemesis so far, obviously," Leyland said. "A home run with a couple of guys on, that's hurt us in all of our games really up to this point."
With a crowd of 46,593 looking on, the Orioles continued their solid play under manager Buck Showalter. Baltimore went 34-23 after Showalter took over last year, and the offseason acquisitions of Derrek Lee, Vladimir Guerrero, Hardy and Mark Reynolds have Orioles fans hopeful that the team's run of 13 straight losing seasons will end in 2011.
The players are starting to think that way, too.
"We're aware of the talent we have," Arrieta said. "If we go out there and pitch and keep our team in the game, it's only a matter of time before we put some runs on the board. Somebody's going to have the hot hand."
Porcello yielded five runs, nine hits and a walk in five innings.
"He wasn't great, but he was OK," Leyland said.
Baltimore went up 1-0 in the second inning when Wieters hit a leadoff double and scored on Porcello's two-out wild pitch.
Detroit pulled even in the third. After Brandon Inge doubled and scored on a single by Rhymes, Cabrera flied out with two outs and two on.
The Tigers got only two runners in scoring position the rest of the way.
- Former Orioles manager Earl Weaver threw out the ceremonial first pitch to Showalter.
- RF Magglio Ordonez started for Detroit after missing Sunday's game with a sore right ankle. He snapped an 0-for-9 start with a fifth-inning single.
- Baltimore is 38-20 in home openers, including 5-0 against Detroit.
- Orioles pitcher Jeremy Guthrie was hospitalized Monday with a high fever and will be replaced by Brad Bergesen as the starter Wednesday.