The Cubs reinstated Roberts (forearm) from the 15-day injured list Sunday and optioned him to Triple-A Iowa, Vinnie Duber of the Chicago Sun-Times reports.
Roberts had been shelved since June 29 due to forearm inflammation but is back to full health after completing a six-appearance rehab assignment at Triple-A. The Cubs don't have a spot available for the right-hander in the big-league bullpen, so he'll stick around at Iowa for now.