[Luke]

If you want something that can be rolled up it is not going to work nearly as well as a permanent soundproofing material. The only thing that comes to mind is to weatherstrip the door really well. Weatherstripping is important but if you want to do a better job insulate the door also with as much material as possible. The more mass the more sound gets stopped. But if there is a crack in the door the insulation won't do much because the sound will be able to escape, that's why you need to weatherstrip. (and make sure there are no cracks in the door)