With scrollviews, you don't give them an orientation exactly. You set their frame and their content size. So if you set the frame to 1024 x 768 and the content size is 3000 x 768, the scrollview will automatically allow scrolling horizontally. And because you set the frame to a landscape ratio/size, the scrollview will be in a landscape "orientation." Pseudo code below to help.
UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0,0,1024,768)];
[scrollView setContentSize:CGSizeMake(3000, 768)];
Let me know if this doesn't help and I can elaborate or help further.