An African website reported that the midfielder was in fact 42 and had forged identity documents in a bid to embark on a career with the Italian capital club's youth side.
The claims sparked an investigation in Italy, with the teenager quizzed by Serie A's federal prosecutor, but a ruling on Wednesday cleared the Cameroon prospect of any wrongdoing.
A statement read: "The Italian FA has confirmed that Lazio youngster Joseph Minala is 17 and not guilty of age fraud, as alleged back in February.
"There are no doubts about his age. He is 17."
Age fraud has become an increasing problem within African football. Nine players were excluded from the African Under-17 Championship in Morocco after MRI wrist scans showed them to be over the age limit.
Congo, Ivory Coast and Nigeria each had three players banned, while later that year the Super Eagles lost several players from their Under-17 World Cup squad for the same reason.