Roberts can remain on leave for a maximum of three days.
To fill Roberts' roster spot, the Orioles have reinstated pitcher Steve Johnson from the 15-day disabled list. Johnson will serve as an extra reliever in Roberts' absence.
Johnson, on the disabled list since June 6 with a strained left oblique, was 1-2 with a 5.49 ERA in four starts at Triple-A Norfolk. He threw two shutout innings with the Gulf Coast League Orioles to start his rehab assignment and allowed two runs in six innings in two starts with short-season Single-A Aberdeen.
Johnson was scheduled to continue his assignment on Saturday at Double-A Bowie. Instead, he will report to Camden Yards.
Ryan Flaherty is starting at second base tonight while Roberts remains at the hospital.
Roberts, 35, is batting .245/.283/.357 in 30 games for the Orioles this season. Johnson, 25, is 1-1 with an 8.49 ERA in five games, including one start.