Your original code uses three transforms, you've now tried to do it with two. Just go back to three (using distinct variables to make it clear):
NSAffineTransform *pos1 = [NSAffineTransform transform];
[pos1 translateXBy:-1*centerX.doubleValue yBy:-1*centerY.doubleValue];
[path transformUsingAffineTransform:pos1];
NSAffineTransform *rot = [NSAffineTransform transform];
[rot rotateByRadians:rotation.doubleValue / 180 * M_PI];
[path transformUsingAffineTransform:rot];
NSAffineTransform *pos2 = [NSAffineTransform transform];
[pos2 translateXBy:centerX.doubleValue yBy:centerY.doubleValue];
[path transformUsingAffineTransform:pos2];
If you wish to just use one transformUsingAffineTransform:
you can delete the three uses above and add the code:
[pos1 appendTransform:rot];
[pos1 appendTransform:pos2];
[path transformUsingAffineTransform:pos1];
You can even do it with one, but note the order - work from last to first:
NSAffineTransform *compound = [NSAffineTransform transform];
[compound translateXBy:centerX.doubleValue yBy:centerY.doubleValue];
[compound rotateByRadians:rotation.doubleValue / 180 * M_PI];
[compound translateXBy:-1*centerX.doubleValue yBy:-1*centerY.doubleValue];
[path transformUsingAffineTransform:compound];
HTH