Interim coach Grant Brebner named four teenagers in his starting XI for the clash at Sydney's Netstrata Jubilee Stadium as Victory ended an unwanted club record four straight defeats.
It had to be patient as Perth controlled most of the early possession but Rojas leathered in a 25-yard effort into the top-right corner to get it up and running.
Tarek Elrich dragged down Andrew Nabbout on the hour, with the winger converting the penalty he won, before Rojas's composed finish – his fourth goal in two games – meant it was game over.
Elvis Kamsoba scored his first A-League goal in injury time to complete proceedings, as Victory, which is guaranteed to finish 10th with just one game to play, returned to winning ways.
Glory's third loss in five since the season resumed means its spot in the top six is still not officially locked in, although its finals place will be confirmed if Adelaide United do not beat Melbourne City on Tuesday.