McLeod tapped in the opener just four minutes after coming on as a 36th-minute substitute before superb half-volleys from Daniel Powell and sub Stephen Gleeson sealed a first win in nine games for the Dons.
The stadium:mk hosts were twice denied by the woodwork in a dominant first-half display, with Dean Bowditch curling a 25-yard free-kick against the post and Ryan Lowe heading against the crossbar from close range.
Rovers midfielder James Harper then had a goal disallowed for a shove before McLeod put Karl Robinson's side ahead in the 40th minute, slotting in the rebound after Lowe's fierce shot had been parried by goalkeeper Gary Woods.
Powell celebrated his new two-year contract by doubling their lead in the 56th minute, swivelling to fire a stunning left-footed half-volley into the top corner from the edge of the box.
Doncaster striker James Coppinger had a shot deflected just wide and then fired another decent chance too close to Dons keeper Ian McLoughlin as the visitors rallied.
But Gleeson marked his return from a three-month injury lay-off by scoring with his first touch seven minutes from the end, blasting McLeod's knock-down into the corner as Rovers missed the chance to go four points clear at the top of the League One standings.