Many displays can do the scrolling for you, problem is: We're not telepathic and don't know what display you have.
The term 16x2 would generally lead one to believe that he is using a character mode LCD controlled by an HD44780 type controller. As he has discovered, this controller cannot inherently shift one line without the other and I don't know of any libraries that do this in software.
A similar but possibly easier approach than the buffer idea (depending on the application) would be to shift both lines and then rewrite the line that you didn't want to change.
Note that I use the term 'shift' instead of 'scroll' because that's how it is described in the LCD controller data sheet. For some insight into the problem check out the LCD Addressing link at http://web.alfredstate.edu/weimandn.
Don