I had a roof box on my previous bongo with no problems raising the roof..
mine was a cheapo thing from Motor World and my roofrack was a lightweight GRP one designed for the AFT and I suppose it depends on its weight as to need a little helping hand to get it fully up...
As Bob says..welcome to Bongo Fury..

..you will find a wealth of information on this forum so don't be afraid to ask what might seem to be a daft question because we have all thought that at sometime.
Good luck with you adventures...
Alan