Wrexham keeper Michael Ingham made important early saves, diving full length to turn Paul Tait's low shot for a corner and then tipping Gary Jones' effort over the crossbar.
Rickie Lambert fired a long-range free-kick straight at the home keeper before Gary Jones crossed and Tait got inside his marker for a free header to put Rochdale into the lead after 21 minutes.
Wrexham went close when Mark Jones lobbed keeper Matt Gilks and Tony Gallimore cleared off the line.
Ingham then had to pull off a spectacular flying save to keep out Lambert's glancing header form Ernie Cooksey's cross.
A controversial penalty put Wrexham level just before half-time. Referee Gary Sutton ruled that Gareth Griffiths had pushed Dennis Lawrence and Matt Crowell stepped up to send Gilks the wrong way from the ensuing spot-kick.
Crowell then came to the rescue, heading off the line from Lambert before Blair Sturrock saw a shot blocked by the keeper's legs.
Then Sturrock was worked clear and seemed sure to score, but Lawrence challenged and hooked the ball away.
An innocuous long clearance upfield after 65 minutes seemed no danger to the visiting defence, but Ferguson pounced on the loose ball 25 yards out and unleashed an unstoppable shot that gave Gilks no chance.
Jon Walters almost added to the hosts' lead but shot wide when he might have scored.