Two second-half goals were enough to see Chelsea into the fourth round of the Carling Cup at Blackburn's expense.
Cole finished from close range to break the deadlock
Joe Cole celebrated his first start of the season by converting Salomon Kalou's cross after 53 minutes.
Kalou tapped in the second after Brad Friedel had parried substitute Shaun Wright-Phillips' shot.
Blackburn had their chances in an entertaining tie, with Shabani Nonda looking particularly lively, but Chelsea were too strong.
Rovers boss Mark Hughes, in his 100th game in charge, also saw Nonda and Morten Gamst Pedersen pick up injuries.
It was Nonda who had the first chance of the game, the striker bursting through before sending his effort narrowly wide.
But Chelsea got into their stride, with the lively Kalou and Arjen Robben going close.
Blackburn almost took the lead in the 41st minute when Pedersen rattled in a free kick from distance but Hilario turned the ball around the post and it was scoreless at half-time.
Pedersen limped off in the 48th minute and Rovers' plight worsened five minutes later when Cole put Chelsea ahead - although the hosts were convinced the England midfielder had handled the ball in the lead-up to the goal.
Nonda was then stretchered off after a collision with John Terry, who later had a header scrambled away.
A minute after coming on, Wright-Phillips delivered the killer blow to Blackburn's hopes of recovery.
Brad Friedel did well to parry the winger's fierce effort in the wet conditions but Kalou raced in to fire home the rebound.
Blackburn manager Mark Hughes on a possible handball in the lead-up to Cole's goal:
"We are a little bit disappointed as we tried to highlight it to the officials.
"But they obviously did not see it or they would have given it.
"We were just trying to find our shape and unfortunately for us the ball ends up in the back of our net."
Chelsea assistant coach Steve Clarke:
"Everyone is pleased to see Joe back.
"He had a nasty injury pre-season and it took him a little time to get over it.
"It was a difficult time for him and it is good to see him back on the pitch. It was certainly nice for him to get a goal. Now he has to get match fit."
Blackburn: Friedel, Emerton, Khizanishvili, Henchoz, Neill, Bentley, McEveley, Mokoena, Pedersen (Peter 49), McCarthy (Jeffers 86), Nonda (Roberts 56).
Subs Not Used: Brown, Todd.
Booked: Bentley, Peter.
Chelsea: Hilario, Geremi, Terry, Boulahrouz, Ashley Cole, Joe Cole (Wright-Phillips 79), Essien, Ballack (Lampard 61), Makelele, Robben (Drogba 83), Kalou.
Subs Not Used: Makaba-Makalamby, Ricardo Carvalho.
Booked: Joe Cole, Boulahrouz.
Goals: Joe Cole 53, Kalou 81.