The club who Robson guided to the FA Cup and UEFA Cup comfortably took the points against Millwall with three goals in the final half-hour.
Millwall were their own worst enemy after a mistake from Jack Smith led to Shane Lowry diverting into his own net and then centre-back Mark Beevers got the final touch to Paul Anderson's header for the third.
In between, a powerful header from Tommy Smith crashed into the roof of the Millwall net as Ipswich got over their shock Capital One Cup exit at the hands of Stevenage.
The scoreline did not flatter the hosts, who should have gone into the interval at least one goal to the good after shading the first half.
Striker David McGoldrick was their dangerman, going close on three separate occasions.
After just five minutes, the Town striker got on the end of Cole Skuse's looping through ball but his attempts to round Stephen Bywater were thwarted by the Millwall keeper.
McGoldrick then went close in the 17th minute when he met Aaron Cresswell's teasing inswinging free-kick but saw his header sail agonisingly wide of the far post.
All Millwall could muster was a 25-yard shot from James Henry which failed to trouble Scott Loach.
McGoldrick's best moment of the first half came in the 34th minute and was all of his own making. Outmuscling Beevers, he twisted and turned past Lowry before firing a goalbound shot that was superbly tipped away by the outstretched Bywater.
Millwall showed more fight in the early stages of the second half with Richard Chaplow heading a great chance wide following good work from new loan signing Shaun Derry on the by-line.
But their early second-half promise was quickly undone by a moment of hesitation from Smith.
Dithering in his own area, the right-back was dispossessed by Cresswell, whose low cross was blocked by Bywater but only into the path of the unfortunate Lowry for an own goal.
In the 70th minute, the game was all but over as Ipswich doubled their lead. A needless free-kick was given away by Lowry near the corner flag and it proved costly as Smith rose highest to powerfully head home Anderson's delivery.
And it was three with eight minutes left as a patient build-up saw Elliott Hewitt cross and Anderson head home via a deflection off Beevers.
It could have been even worse for the Lions after Manchester United loanee Ryan Tunnicliffe burst clear but his shot lacked the power to beat Bywater.