Ricketts joined Bolton from Hull at the weekend and needed just 28 minutes to open his account in a Wanderers shirt, the defender heading home from fellow new boy Sean Davis' inch-perfect cross.
Megson, who also handed a debut to former Aston Villa defender Zat Knight, saw his side go further ahead after 57 minutes when captain Kevin Davies tapped home from close range after good work by Matt Taylor. Den Bosch pulled a goal back with a deflected effort off Gavin McCann 10 minutes from time, which looped over substitute goalkeeper Adam Bogdan.
Wigan's preparations for the new Barclays Premier League season continued with a thumping 4-1 victory against Coca-Cola Championship side Preston at Deepdale.
Goals from Hugo Rodallega and Charles N'Zogbia had the Latics in the driving seat at the interval while a third from Michael Brown and a debut strike by Jason Scotland sealed an emphatic win for Roberto Martinez's side in the second half.
Neil Mellor pulled one back for the hosts in the dying minutes.
Premier League new boys Burnley were held to a 2-2 draw at League Two side Accrington.
Goals from John Miles and Sean McConville had the hosts ahead with a quarter of the match remaining, but Robbie Blake pulled one back for the Clarets after 83 minutes before Owen Coyle's men levelled late on through Steven Thompson.