The move dropped him 3 1/2 games in the American League West standings.
"That's all right; we've got a lot of season left," Rosales said. "It's still a good feeling. I'm looking forward to everything this opportunity will bring."
The Rangers acquired Rosales because they wanted another versatile player on the bench. He can play all four infield positions and has appeared in eight games as an outfielder. He joins Jurickson Profar and Jeff Baker in giving the Rangers three players off the bench who can play in the infield or the outfield.
"It just adds another versatile piece to the mix," assistant general manager Thad Levine said. "We've always admired how hard he plays the game. He plays with a ton of energy and enthusiasm. He was a Texas Ranger playing for the Oakland Athletics. He finally found his rightful home."
T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, and follow him on Twitter @Sullivan_Ranger. This story was not subject to the approval of Major League Baseball or its clubs.