It is the third position Hook has been utilised in as many games in this year's Championship.
Elsewhere 2009 Lions tourist Leigh Halfpenny returns to the match-day squad after recovering from the ankle injury that kept him on the sidelines for Wales' two previous encounters.
"We have selected the strongest possible side, showing the utmost respect to Italy," said Wales head coach and former Lions forwards coach Warren Gatland.
"We know only too well what tough opponents they are in Rome and so we have picked the strongest team available to us."
There are no changes in the forwards with Wales looking for more of the same from their pack which performed so well in Murrayfield.
"This is very much a vote of confidence for the forwards, they have been going extremely well as a unit and we are looking for more of the same against Italy," said Wales backs coach Rob Howley, a Lion in 1997 and 2001.
"Our hand has been forced in the back line, Jonathan is simply not ready this weekend after struggling with his hamstring since the Scotland game.
"The obvious decision then is to move James into the centre where he has done well in partnership with Jamie.
"And bringing Stephen Jones in at fly half is a great luxury to have. He was hurting after the England game, he will be looking forward to getting back out there and we are very happy to have that option available to us."
The win in Scotland was the Dragons' first taste of victory in nine games. Italy were demolished at Twickenham in round two of the Championship but Howley is expecting a much tougher prospect as Wales look to build on their latest triumph.
"Italy are a different animal at home, they showed that against Ireland," added Howley.
"Since the inception of Italy as a part of the Six Nations they have continued to improve year on year and they are always capable of turning you over.
"We are under no illusion as to how tough it is going to be for us out there on Saturday, history shows us that it is going to be a very hard day at the office, but we have picked a side to go out there and win."