Well no one has responded to this so I guess I'll give you my opinion on how this should be done.
Some may say to use the Title Tool that comes with Premiere, I believe the manual suggests this even. I find that tool sucky and clunky.
A prettier and much more flexiable way of doing so is done with two things:
A large bitmap image & the Image Pan effect.
Make a large bitmap, how large depends on your video. What you want is the image to be the same width as your video, but atleast 3 times as high.
You'll place your credits in the middle, with the top and bottom portions being a solid color of your choice(most likely black).
Here's a image I made :
Pretty freakin' huge.
You take this into Premiere. Drag it to the timeline and then add the "Image Pan" Effect(located under transform). Enable keyframing, then move the scrub line to the begining of the clip/image. Hit setup on image pan. Hold down the Alt key, this makes it keep the proper aspect ratio so it doesn't look squished, the box should turn into a rectangle at the top of the image.
Just hit OK. Then goto the end of the clip. Hit Setup on Image Pan again, hold down alt again, this time drag the rectangle to the bottom of the image.
Now preview your project. It should make the image scroll.
You can adjust the length of the clip to make it scroll smoother.
I also added some music and adjusted the transperancy rubber bands to get a nice fade in/fade out effect near the end.
<a href="http://home.attbi.com/~klinky/comp-demo.avi">My demo movie</a>.
Hope this helps
~klinky