Rochina had struggled to make an impact at Ewood Park, making just five appearances for Rovers this season, after spending last season on loan at Real Zaragoza.
The Spaniard has made a total of 56 appearances for Rovers throughout his three and a half years at the club, netting just 11 goals. The 22 year-old will now hope to stave off relegation from La Liga with 19th placed Vallecano, who are just three points away from climbing out of the relegation zone.
Vallecano announced the signing earlier today and confirmed Rochina will be unveiled to the press on Tuesday.
A club statement read: "Ruben Rochina is officially a Rayo Vallecano player until the end of this season, on loan from Blackburn Rovers.
The club (also) reserves a purchase option at the end of the current campaign."