Here's some code I used in iDork to rotate and position iAds:
#define DEG 0.0174532925
#define DEGREES_TO_RADIANS(__ANGLE__) ((__ANGLE__) / 180.0 * M_PI)
adView = [ [ ADBannerView alloc ] initWithFrame: CGRectZero ];
adView.requiredContentSizeIdentifiers = [ NSSet setWithObject:ADBannerContentSizeIdentifier480x32 ];
adView.currentContentSizeIdentifier = ADBannerContentSizeIdentifier480x32;
CGSize windowSize;
windowSize.width = 480;
windowSize.height = 320;
adView.transform = CGAffineTransformMakeRotation ( DEGREES_TO_RADIANS ( 90 ) );
adView.center = CGPointMake ( adView.frame.size.width / 2, windowSize.width / 2 );
self.adView.delegate = self;
adView.hidden = YES;