We now know the corresponding roster move the Twins have made for sending left fielder Eddie Rosario back to AAA: Robbie Grossman. If your reaction to that is "who?", you aren't alone. The Twins just signed Robbie Grossman to a minor league contract yesterday.
Grossman served as an outfielder for the Houston Astros for three years, but was never quite a full-time player. He has major-league experience at all three outfield positions. He had signed a minor league contract with the Indians this year, but it had an opt-out date earlier this week and he opted-out. Grossman had an opt-out date of June 15th with his new Twins deal, but it looks like that won't be utilized (for now).
Grossman, unlike David Murphy, is only 26 years old. It is likely he will accept this major league assignment with the Twins.