Rooker was recalled from Triple-A El Paso on Friday.
The 27-year-old hasn't yet appeared in any major-league games this year, but he'll join the Padres as outfield depth after Jurickson Profar (concussion/neck) was placed on the injured list. Rooker has slashed .279/.401/.596 with 14 homers, 45 runs, 44 RBI and four stolen bases over 49 games in El Paso this year.