A former defender who quit at 25 with a knee injury in 2001, Rojas will referee in the first division for the first time.
Rojas, whose only club in his playing days was first division Cobresal, won promotion to the top flight as a referee this year after several seasons officiating in the second division.
"This always appealed to me but I had two right knee operations (for torn ligaments) that made it difficult for me to continue playing," Rojas told Reuters in an interview.
"This option of refereeing appeared spontaneously and so far it's been a good choice, I think," he said.
Rojas said his footballing past gave him some advantages, even if judgment of his refereeing can be harsher as a former player as happened to him in the second division.
"Relations with the players are very good... also, because of having been in many changing rooms and situations that happen on the pitch, you can see them differently," he said.
Few players have gone on to referee, the last in Chile being Domingo Massaro who played for his country at the 1952 Olympic Games.
Uruguayan Dario Ubriaco, a former under-20 international, became a top flight referee in 2004 and four years later reached international level.
The 34-year-old Rojas does not yet know which match in the Apertura championship, first of two in the season, he will be handed this weekend.
He said he would have no problems refereeing match involving Cobresal but he hoped his impartiality would not be more severely called into question if he made mistakes.
"I'm a professional in football and I'd like to referee them but the authorities make the decision," Rojas said.
