I would keep the roof on to respray but put it up,that can all be masked up & still get to most of the metal,unless the roof is loose or needs repair if you have a look at woolfy's pic's one of the vans ?? on there have got the roof off down to the wood frame. If you do decide to remove roof get step by step photo's of it then you can show us & refer to them when putting it back together no one seems to have done this before [:0]
Sybhil & no1