Things got off to the worst possible start as Craig Bellamy beat his man and whipped in a dangerous cross for the unmarked Seyi Olofinjana to head in at the far post to ease the Cardiff nerves.
Rocha then ensured Pompey would have the proverbial mountain to climb after being needlessly throwing his head towards Jay Bothroyd, resulting in an instant red card which is the normal punishment for such an offence these days.
The Portuguese defender will now miss the final four games of the season for receiving his second red card of the season, which adds an extra game to the three a player would usually receive for violent conduct.
Olofinjana should have doubled the Bluebirds' lead as the Pompey defence didn't learn their lesson and Bellamy crossed for Olofinjana again but he somehow placed his header wide.
Steve Cotterill's ten men were clearly struggling to create anything, with David Nugent's header over the bar from De Laet's cross being the only real chance in the first half.
However, the defence had worked hard to contain Cardiff but were undone in first half stoppage time when Jamie Ashdown initially parried Bellamy's header away only for Bothroyd to tap the loose ball home.
The second half was a quiet affair with Cardiff happy to keep the ball and Pompey happy to sit back and let the game pass them by.
The hosts sealed the points when Bellamy again beat his full back and crossed for the onrushing Peter Whittingham who had the simple job of blasting the ball into the net from close range.
Danny Webber could have given the travelling Pompey fans something to cheer about when he came on as a substitute but struck his shot against the side netting and then flicked Halford's cross tamely wide.
There was a sense of deja vu when the final whistle blew. Rocha had been sent off and unfortunately there was some crowd trouble as Pompey fans began fighting, much like at Reading a fortnight ago. Stewards and the police got involved as some of the fans were embarrassingly turfed out for their violent behaviour.
All in all, this was another poor performance and the season cannot end quick enough now. Pompey are safe so that is "mission accomplished" but we're now becoming painful to watch as the players have nothing to play for and many of them don't know where their futures lie.
With games against promotion chasing Swansea, Burnley and Norwich to come and the final game against a Scunthorpe side that may still have a shout of survival, it's quite possible that Pompey will lose all of their remaining games.
It's up to Steve Cotterill to ensure that doesn't happen and Pompey can head into the close season with some optimism as another summer rebuilding job looms.
Pompey Player Ratings
Jamie Ashdown: 6 - Can't be blamed for any of the goals.
Ritchie De Laet: 5 - Struggled with the pace of the Cardiff attack.
Ricardo Rocha: 3 - Stupid red card made task much harder.
Greg Halford: 5 - Too static overall.
Hermann Hreidarsson: 5 - Off at half time following a knee injury.
Liam Lawrence: 5 - Didn't get in the game.
Joel Ward: 7 - Worked hard when covering two positions at times.
Jonathan Hogg: 5 - Lost the ball too often.
David Cotterill: 5 - No joy on the flanks for Swansea loanee.
David Nugent: 5 - Posed little threat and withdrawn early.
Dave Kitson: 5 - Spent much of the game tracking back and trying to win long balls.
Substitutes
Darryl Flahavan
Aaron Mokoena (Hreidarsson 46): 6 - Did OK when replacing Hermann.
Carl Dickinson (Nugent 62): N/A - Solid enough.
Nadir Ciftci
Kanu
Danny Webber (Cotterill 64): N/A - Had a couple of good chances.