EXCLUSIVE

"The Vampire Diaries" star Zach Roerig just won sole custody of his 2-year old daughter -- from the jailed woman he wanted to pay him child support. " starjust won sole custody of his 2-year old daughter -- from the jailed woman he wanted to pay him child support.

Roerig was awarded custody last month in Georgia ... and a judge signed off on Zach making all future decisions for his daughter -- according to court docs.

We broke the story -- Roerig told the court he wanted child support from his ex back in July ... but it looks like he has since backed off the request.

Maybe it's cause he makes 30k a month from the TV show -- and she makes, well ... nothing.