Arano arrives from Racing Club, while Menegazzo has signed from Juventude to end Siena's long hunt for the pair.
Siena almost saw their move for Menegazzo thwarted by a rogue agent acting on behalf of the player, but they finally reached an agreement to sign the midfielder.
Menegazzo admitted he was looking forward to playing in Italy after the difficulty surrounding his transfer.
"For the experience I have, I hope to be able to give my help to the team in the best possible way," said Menegazzo.
Arano also sees his move to Italy as a big challenge for himself.
"This is a very important step for my career because the Italian Championship is one of the most important," said Arano.
