He was pushed hard by the Serbian fourth seed in the rain-delayed semi-final but improved his record against Djokovic to 9-4 as he controlled the key moments.
The 19-year-old had earlier kept her nerve to see off eighth seed Svetlana Kuznetsova in a hard-fought three-setter lasting two hours 40 minutes in blazing temperatures.
Elsewhere, the No. 4 seed Juan Martin del Potro was forced to save three match points during a hard fought 4-6 6-4 7-6 victory over Cypriot Marcos Baghdatis .
Sixth seed Roddick, who lost the 2004 and 2005 finals to Federer, was pushed hard before beating Jurgen Melzer 7-6 (7-2) 7-6 (7-2) 4-6 6-3 after almost three hours on court.
Officially known as the West Indian Locust, the stinking toe tree produces a seed pod that looks like a big, brown toe and also smells like one when the hard outer shell is cracked open.