Yeah, I like the Roll, too -- it's a rather unconventional hybrid that appeals to me, and mostly for the reason (it's a little weird).

Hmm -- an "integrated" headset may or may not offer a pathway for upgrade. Integrated headsets mean the bearings just sit right in cups in the frame; they do not use separate cups. Whether or not you could convert that to a threadless system, I don't know. They certainly have integrated threadless headsets, but I think you'd need to find one sized exactly for your head tube cups (whatever size they are). I think maintenance is easier on these, but upgrading may be more difficult. I'd ask in the "Bicycle Mechanics" forum here on Bike Forums -- those guys will know more about that topic in general (potentially upgrading integrated headsets).

They'll likely ask what your purpose is -- what benefit are you seeking from changing out the quill stem?