Doncaster have made forward Dany N'Guessan their sixth summer signing.
Tottenham have confirmed that Romanian defender Vlad Chiriches has completed a move to Napoli.
The Serie A side announced the move on their official website on Wednesday night, with Rovers doing likewise once the deal was ratified.
The Argentinian midfielder, who is under contract at Ewood Park until summer 2014, will remain with Palermo until June 30.
Formica, 24, joined Blackburn from Newell's Old Boys two years ago and has scored five times in 54 appearances.