In my opinion, the reason to foil a roll is primarily to speed up the cook. I've had them take 24 hours before - foil can speed it up. But, taking advice from others here on this board, I poke quite a few holes in the bottom so the fat can drain.
If time isn't an issue, I don't see a need to foil at all. It's such a fatty piece of meat that I don't find it needs it to retain moisture. But, that's just my opinion.