Celtic were knocked out of the League Cup in the semi-finals by StMirren at Hampden last Sunday but there was little chance of another shock, although the breakthrough did not come until the 56th minute when Commons scored from the spot after he was fouled by Raith defender Simon Mensing.
First Division side Rovers ran out of steam and in the 82nd minute Forrest, on for Tony Watt, grabbed the second goal, with Mulgrew's fine strike four minutes later completing a solid afternoon's work by the visitors.
Very good one for Celtic FC, they deserve their win totally. Good set of players they've got