Right-hander Samuel Deduno was also outrighted to Triple-A Rochester and taken off the 40-man roster. The Twins now have 33 players on their 40-man roster.
Roenicke, 30, posted a 3.25 ERA in 63 appearances with the Rockies last season. He struck out 54, walked 43 and gave up nine homers in 88 2/3 innings.
Roenicke, the son of former Major League outfielder Gary Roenicke and the nephew of Brewers manager Ron Roenicke, has a career 4.09 ERA in parts of five seasons. The 6-foot-3 right-hander has struck out 123 and walked 81 in 158 1/3 big league innings.
Field, 25, saw action in two games with the Rockies last season, going 0-for-2 at the plate, after hitting .271 in 16 games with the Rockies in '11. Field, who can play shortstop, second base or third base, hit .246/.315/.400 with eight homers and 49 RBIs in 121 games with Triple-A Colorado Springs last year.
Casilla leaves the Twins after parts of seven seasons in Minnesota as a second baseman and shortstop. The switch-hitter batted .241/.282/.321 with one homer and 30 RBIs in 106 games last season.
Casilla, 28, is a career .250/.305/.334 hitter in 515 games with the Twins. His biggest hit came in 2009 -- a walk-off single in Game 163 against the Tigers in the Metrodome to clinch the American League Central title.
But he was likely to be non-tendered by the Twins this offseason, as he was due to make approximately $1.8 million in arbitration after making $1.38 million last season.