Rebellin, who won the Amstel Gold Race, La Fleche Wallonne and Liege–Bastogne–Liege in a stellar 2004 season, died aged 51 after being hit by a truck while training near the northern city of Vicenza on Wednesday.
"Our relentless investigations... have allowed Vicenza Carabinieri police to put a face and a name to the driver of the heavy goods vehicle that ran over and killed Davide Rebellin," police colonel Giuseppe Moscati said in a statement.
The suspect was driving a Volvo truck with a German licence plate, the Vicenza prosecutor's office said in a statement.
He initially got out of his cab after the crash to approach the victim, who was killed instantly, but then drove away, it added. Other people at the scene took the driver's photo which helped the authorities to trace him to a location in the region of North Rhine-Westphalia.
Prosecutors said they would continue their investigations before deciding what further action to take.
Rebellin, who was ordered to return his road race silver medal from the 2008 Olympics in Beijing after a retroactive doping test, retired earlier this year after three decades in professional cycling.