1. Create your Credit Roll in Illustrator/Photoshop
2. Import the Credit Roll to After Effects
3. use the handy preset "Drift Over Time". set the direction to 0 degrees and the speed to an amount that's an even multiple of your frame rate to avoid judder*. for example for 25fps try speed of 50.
* about text judder: speed is not the only factor, you should also choose a proper font that is not to thin. sans serif font's usually do well. you can also add reduce flicker to introduce some blur if there is still a judder in your text. handy resources here: FAQ: Why does horizontal motion stutter (judder) in my movies, such as during pans?