Both Juve and Napoli have a 100% record in the Italian championship this campaign after two rounds of matches, with Lazio too having won both their matches.
"The two most complete teams I have seen are Juventus and Napoli," Rossi told Corriere dello Sport. "They both followed a strict philosophy.
"Napoli took a certain type of young player, and that will come in handy not only now but also in the future. Juventus have always targeted players who are already 'built'.
"Fiorentina did the only thing they could do - initiate a total revolution. Roma have also recruited well."
Rossi is currently without a club after being sacked by Fiorentina in May.