Wigan have announced Uwe Rosler as their new manager after agreeing compensation with Brentford.
Arsenal manager Arsene Wenger feels loan deals should be treated just like permanent transfers.
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.