The Brazil international has emerged as a much sought-after commodity after shining for club and country.
With Jurgen Klopp set to be in the market for a new keeper this summer, Anfield has been mooted as a possible destination for the 25-year-old.
French giants Paris Saint-Germain are also said to be keen, but any club plotting an approach has been warned that they will need to dig deep in order to get a deal over the line.
Ex-Roma goalkeeping coach Negrisolo told Il Romanista on the South American star: “Is Alisson worth €50m? Don’t be silly, he’s worth far more than that.
“I don’t think many people have realised who Alisson is. This guy is a phenomenon. He is the number one of number ones. He is the Messi of goalkeepers, because he has the same mentality as Messi. He is a goalkeeper who can mark an era.
“There is absolutely no comparison with Gianluigi Donnarumma, because Alisson is extraordinary. The first time I saw him play, he wasn’t yet on the Roma books. I watched him play for Brazil and he made an enormous impression on me.
“The way he behaves in the goal, he reminds me of Dino Zoff. I’d also compare him to Michel Preud-Homme, who had the class of someone born to be a goalkeeper.
“I told Alisson when I met him at Roma’s Trigoria ground that he was born for this. He was already strong when he arrived, but has improved even more since he has been in Italy, especially when coming out low to get the ball. Now he is far more decisive in those situations.
“I have to give credit to Marco Savorani, the current Roma goalkeeping coach, who used to work under me. Savorani also helped Wojciech Szczesny improve a lot and Juventus got themselves a bargain buying him from Arsenal.
“I know goalkeepers, that is my business, and I can assure you Alisson can be a guarantee for at least another 10 years. He’s already a hero to the fans and Roma need to keep hold of him.
“Alisson is crucial off the field too, as you can see he has the mind of a coach. Look at the way he moves and acts when the ball is in his hands and you’ll understand.”