Rossi was a junior player at United before being sold to the Spanish outfit.
Giggs told Calciomercato.com: "It's Giuseppe Rossi. I know him very well. He's very good and he's a good guy. He grew up with us. Everyone loved him and Sir Alex admired him, and admires him so much now.
"The only problem with Manchester United was (Ruud) Van Nistelrooy. How do you hold onto a striker who plays well but is still very young."