The 30-year-old Roenicke had a 3.25 ERA in 88 2-3 innings last season for the Rockies with 43 walks and 54 strikeouts. He's the nephew of Milwaukee Brewers manager Ron Roenicke and has also pitched for Cincinnati and Toronto.
The 25-year-old Field has appeared in 18 major league games. He played last season for Triple-A Colorado Springs.
Casilla had several chances in the last five years to be the regular second baseman, but he couldn't stay healthy or consistent enough.