Rovers have agreed to let him spend the rest of the season with Vallecano.
Rovers boss Gary Bowyer told the club's website: "Obviously we are seeing it as an opportunity for him to go out to Spain and get games.
"His injury on the opening day of the season set him back with us. So we've agreed it will be good to get him playing some games and we'll pick it back up in the summer.
"Playing in his native Spain appeals to Ruben, so we'll monitor his progress."
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