Do you mean automatic scrolling like in most games/movies or do you mean that the Credit-Screen itself can be scrolled via Touchinput.
For the first one (one method off millions, I guess):
- make one NGUI-Label for the whole Credits or for every Name/Word a single Label
- create an empty GameObject -> make this Object the parent of the labels
- attach a script to the GameObject where you move it constantly up/down/whatever
For the other one you could create a Scroll-View-Panel. In fact, you could make the first one a Panel, too. So you could use Clipping (Soft Clipping) which would look nicer.
Long answer short: yes, it is possible.