Yeah, you do not want a roll up door. They are loud and impossible to insulate or seal. The one way I think a roll up door could work is if you built a wall a couple feet forward of it giving you a cool roll up 'garage' door for storage/bikes/junk and then a sealed interior.
The key to these is finding one you can put a camper side door in like burlydirtyhippy did over at Expo. You've got to have the right one for the job. The second one you linked is absolutely awesome for all of that exterior storage but no good for adding a door of course.
Another idea for a solo traveler is removing the passenger seat and using that as a walk in door. I personally think living out of just the side doors and rear door would get really old in a camper even though the added side walk-in door takes away from your living space.
I really dig these links. The future is getting brighter. I've been looking at these for awhile and have not seen any new ones in this price range.
I'm sure you already know this but these things are mostly hard to find because they're hard to search for. They're listed in the wrong places on CL, etc. usually and people don't know what to call them. Panel van, box van, box truck, delivery truck, bread truck. With any of these searches you have to wade through a million big moving type trucks and all of the totally destroyed old Penske/Budget rental type trucks.