The Shrimpers made the early running with Robinson firing straight at Saddlers goalkeeper Clayton Ince and the striker latching onto a fine cross-field ball from Alan McCormack before firing over.
But the visitors were reduced to ten men on 14 minutes when former Southend forward Ricketts was shown a straight red card by referee Rob Styles after he lashed out at McCormack.
Walsall went with a 4-4-1 formation with Troy Deeney the lone frontman.
However, any thoughts that Southend could capitalise on their numerical advantage proved wide of the mark.
The Saddlers defended well and restricted their hosts to only a few opportunities as they found the Walsall rearguard a tough nut to crack.
Lee Barnard forced a diving save out of Ince with a 16-yard effort and the shot-stopper then tipped a Franck Moussa header over the bar before the winger fired wide from the edge of the box at the end of the half.
Walsall's chances were understandably more few and far between, with Deeney shooting wide and skipper Stephen Hughes also firing off target.
Southend manager Steve Tilson brought on Francis Laurent at half-time to give his side a three-man attack.
Within five minutes of the restart, the hosts were in front after Robinson squared the ball to Betsy as he advanced down the right channel and fired into the bottom left-hand corner of the goal from 18 yards.
And the hosts made the points safe to end Walsall's six-match winning streak on 72 minutes when Dorian Dervitte passed from the right and Robinson smacked a 16-yard shot into the middle of the goal.
Ince collected a tame Laurent header and saw the striker head wide before the keeper blocked a Robinson shot from point-blank range.