However, an injury to fellow new signing Hayden Coulson, the on-loan Middlesbrough defender, from the same game is not as bad as first feared.

Manager Jim Goodwin said "it is a crying shame" for Roberts.

"When you are that new player, all you want to do is prove to the manager, the staff and the players that you belong here and show the supporters why you have been brought to the club," he said.

"I have been in that position myself as a player. When I first signed for Scunthorpe many years ago, I broke my ankle in one of the first pre-season games and sat out for the next 12 weeks."

Coulson had to go off after being injured in a challenge with Declan Gallagher.

"The scans for Hayden Coulson's injury were actually better than first feared initially," Goodwin said.

"This weekend is going to come too soon for him unfortunately, but he will be back in the squad at the early part of next week."

Meanwhile, Aberdeen have warned their fans over the use of pyro and claim there was £1,000 worth of damage to seats during the win over St Mirren.

The club say 14 pyros were discharged, some of which burnt the pitch and the surrounding turf. One teenager has been charged by police.

More than 40 seats and frames were "vandalised", while the club say an object was thrown at a St Mirren supporters' bus.

"For the past 10 years, St Mirren games have not required a police presence," a club statement said. "As a result of these issues, that is now under review and could change. With that comes yet further unnecessary cost for the club.

"We strongly advise that no balaclavas are worn whilst approaching or within the stadium - this will only attract attention, it unnerves other fans and it's not an image we want to encourage.

"A small, disruptive group is tarnishing the reputation of the club, impacting the match-day experience for others and costing us a lot of money that could be better spent elsewhere."