Inter Milan captain Javier Zanetti has undergone successful surgery on his Achilles tendon and is expected to be out for around six months.
The 39-year-old Argentinian ruptured his left Achilles during Sunday's 1-0 Serie A defeat at Palermo and went under the knife at Pavia's Policlinico San Matteo on Tuesday afternoon.
Professor Franco Benazzo, who performed the operation, told Inter's official website: "The operation was a complete success.
"How long will it take him to recover? He'll have his foot in a cast for the next three weeks and won't be able to walk on it, then he will start to walk in phase two of his physiotherapy.
"As ever in cases like these we're looking at six months out of action."
Benazzo added: "Is there a chance he might lose a bit of fitness after an operation like this? In general terms no, but locally the muscle mass will decrease slightly during the time his foot's immobile.
"But the Inter medical staff have shown over the years that they can get players fit who have suffered from more serious injuries than a snapped Achilles."
The defender, 23, who played six matches during a short loan spell at the New York Stadium this season, has agreed a two-year deal with the Millers.
Rotherham boss Steve Evans told the club's official website: "I think he's been absolutely sensational since he's joined us.
"He's salt of the earth, and he wants to come and work. He wants to improve, and for me he will play in the Championship one day, and he's only 23 now, so we hope that it will be with Rotherham United."
Midfielder Heath and striker Griffiths have both featured for the Saddlers' reserve side this term while goalkeeper Roberts has made the bench for manager Dean Smith's first team.
The trio join fellow youth-team players Matt Preston and Reece Flanagan who signed their professional deals earlier this year.
Smith told the club's official website: "The three lads deserve the opportunity to step up and join Matt Preston and Reece Flanagan in getting a professional deal for the new season.
"The hard work is only just beginning for them but I have every faith in them knuckling down and working hard.
"We've had a really strong youth team this year. The players and staff have worked extremely hard."
