you can rotate chart by some angle by using following code
JFreeChart chart = ChartFactory.createPieChart3D("World Polulation by Countries ", dataset, true, true, true);
PiePlot plot = (PiePlot) chart.getPlot();
plot.setPieIndex(0);
// plot.setLabelFont(new Font("SansSerif", Font.NORMAL, 12));
plot.setNoDataMessage("No data available");
plot.setCircular(false);
plot.setLabelLinksVisible(true);
// plot.zoom(200);
// plot.setStartAngle(180);
// plot.setLabelBackgroundPaint(paint);
plot.setLabelLinkMargin(0.01);
return chart;