Police said Adil Bamaarouf, who had been living in the northern city of Padua, claimed he was planning the attack in retaliation for the fight against the Isis militant group by the EU and US.
He is also claimed to have said that the Italian capital is “the place where Islam must start”.
The deportation order was signed by Interior Minister Angelino Alfano after a report from Ros security police.
Alfano said last week that 259 people had been arrested on terror charges in Italy in 2015, with 67 of them being expelled from the country as a result.