Blackburn signed Formica from Newell's Old Boys for around £3 million in January and, although he appears set to win his first senior Argentina cap this weekend, he has not yet made a first-team appearance for Rovers.
Rochina, who joined from Barcelona in January, has so far made four appearances but all have come from the bench and he has played less than 90 minutes in total.
Nonetheless, Kean remains convinced the duo will be a success at Ewood Park and says their lack of first-team football has been down to the need to adapt to the English style of play.
"I thought they were ready towards the end of the season, it was just about deciding when the best time to put them in was," he told the Lancashire Telegraph. "If we had a couple more victories and were a couple more places higher then it would have been worth putting them in.
"From Mauro's point of view, I certainly felt it was the wrong time to put him. Ruben got a taste of it as a sub but was unfortunate to have dislocated his shoulder because he would have been involved in the Manchester United and Wolves game.
"People have seen what skill and ability that lad has. Mauro has other qualities and both are fantastic talents and I am sure both will do really, really well here.
"They will only be better for a full pre-season. Both of them are solid lads. They have learned English quickly and if you speak to the lads they have been popular figures in the dressing room and have been accepted straight away. They will be all the better for a short break and then coming back for pre-season."