Rojas was optioned to Double-A Reading on Sunday, Todd Zolecki of MLB.com reports.
Rojas was in big-league camp with the Phillies after being added to the 40-man roster in November, but he never had much of a chance of cracking the club's Opening Day roster. The 22-year-old will return to Reading, where he had a .264/.339/.394 slash line with four home runs and 29 steals in 59 games last season.