Santa Cruz has missed Rovers' last five games due to a knee injury and has not featured since the start of March.
The Paraguay striker underwent a minor operation in Germany earlier this week and no date has been set for his return.
Fellow forward Roberts suffered a stress fracture in his foot earlier this month and was initially ruled out for three weeks.
With Blackburn battling to stay in the Premier League, Allardyce is anxious to have both players back at his disposal in a hurry.
"Roque went to Germany and had a little clean-out of the knee and that was very successful," Allardyce told the club's official website.
"There is no long-term lasting damage at all, so hopefully he'll recover as quickly as possible, and then be able to play in some of the games before the end of the season.
"I'm not ruling him out or Jason Roberts either and, obviously, the quicker we can get them back, the better."