Lita showed the Dons' mis-firing strikers how it should be done with cool finishes on the stroke of half time and in the 70th minute - his sixth goal against them this season - after Izale McLeod had given the home side an early lead.
Full-back Leon Crooks curled in a delicious left-foot cross which McLeod coolly steered past City goalkeeper Steve Phillips for his 16th goal of the season after only eight minutes.
The former Derby frontman and Wade Small both missed golden opportunities to extend the lead before the Dons were almost caught on the counter attack when Scott Murray forced Matt Baker into a smart save with his legs.
Small wasted another gilt-edged chance and Phillips denied both McLeod and Dean Lewington from close range before Ben Chorley's header was cleared off the line by Luke Wilkshire.
The robust Phillips then denied Clive Platt with his legs before City predictably made the Dons pay for failing to convert their chances with a 45th minute sucker-punch after an error by Baker.
Wilkshire swung in a hopeful ball which the Dons keeper looked to have covered but he dropped it straight for Lita to ram home the equaliser.
The Dons found Phillips in inspired form after the break when he denied Platt and then McLeod from close range.
The speedy McLeod raced clear of the Robins defence twice more only to waste both opportunities before the lethal Lita grabbed his 24th of the season 20 minutes from the end.
Murray's cross was palmed away by Baker but Wilkshire latched on to it and crossed for the prolific frontman to prod home the winner from five yards to end MK Dons' 12-match unbeaten run at the National Hockey Stadium.