A UIView is always rectangular. However, you can make it look round (or any shape at all, actually) with a mask. To do so, make a UIImage which is a black circle (in a transparent background). Now take the CGImage of that UIImage and make it the contents of a CALayer. Finally, set that CALayer as the mask
of the layer of your view.
Let us suppose that your view is 100 x 100. Then (not tested, but should be pretty much right):
UIGraphicsBeginImageContextWithOptions(CGSizeMake(100,100), NO, 0);
CGContextRef c = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(c, [UIColor blackColor].CGColor);
CGContextFillEllipseInRect(c, CGRectMake(0,0,100,100));
UIImage* maskim = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CALayer* mask = [CALayer new];
mask.frame = CGRectMake(0,0,100,100);
mask.contents = (id)maskim.CGImage;
view.layer.mask = mask;