Rosario, 27, has been active on the transaction wire. The Red Sox acquired him off waivers from the Marlins on Oct. 17, and he was designated for assignment on Nov. 20. Eight days later, he was dealt to the Athletics for right-hander Graham Godfrey. The Athletics then designated Rosario for assignment two days later. On Dec. 10, the Red Sox claimed him off waivers again.
Last season, he combined for 17 saves and a 1.99 ERA in 31 Minor League games between the Marlins' Triple-A, Double-A and Class A teams. Rosario missed nearly two months on the disabled list because of a strained right quad.
He's had limited appearances over the last three seasons with the Marlins, totaling 7 2/3 innings, and made four appearances in June with the big league team. At Triple-A New Orleans, Rosario posted a 1.04 ERA with 16 saves in 25 games, striking out 24 over 26 innings.
This winter, he's been pitching for Gigantes del Cibao in the Dominican, appearing in 12 games through Dec. 8. He has 13 strikeouts and five walks over 11 1/3 innings.
Cubs manager Dale Sveum knows Rosario. Sveum was with Milwaukee when the pitcher made his Major League debut on Sept. 23, 2010, for the Marlins, and the Brewers' Rickie Weeks and Prince Fielder hit his first and third pitches for home runs.
Rosario is the third new arm added to the Cubs' bullpen, joining Japanese pitcher Kyuji Fujikawa, who signed a two-year deal last Friday, and Hector Rondon, who was selected in the Rule 5 Draft.
With the addition of Rosario, the Cubs' 40-man roster is now at 40.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.