No, you do not need Encore, you can do it in Premiere Pro 1.5 that you have.
Goto File/New/Title....
That is where you would input your information to you like your ending credits. To make it roll, where it says Title Type it should be set on Still when you first see it, just change this to Roll. Then click the button right next to that that says "Roll/Crawl Options" when you move your mouse over it. (The next button over to the right is templates if you want to use them.) Click that button to set the rolling credits so they start off the screen and end off the screen if you want it to do that. Save it, drag it to your timeline, test it to make sure that is what you want and your done.
If you need to make changes just double click the Title you just dragged to the timeline earlier and make changes. You can either double click it in the timeline or in your Project window and a new window with your title stuff will come up. Mkae changes if need be and then save it. Since it is already in the timeline (if you dragged it into the timeline before) you don't need to drag it there the changes are already made. Just play it and check it.

Dave