I agree with ThumperD on the roof supports. I'd leave them in if no Full Roll cage is present.
I also have given the center cross brace some thought where the Dome light goes and figured that even though it would probably do nothing much on a roll over, it helps a little to keep the roof in its intended shape. I did remove the Dome light assembly on mine which shaved 3/4 lb.
I only have a 12 point roll bar/Halo in my car, not a cage as some of my well informed friends have indicated in the past.
Roll cage and Roll bar are two siblings of a different Father, one being Big Brother, the other being the brat kid.
In a fantasy no expense sheik type of built, I would some how have the front longitudes, K-member, fender aprons, radiator cross brace, firewall, fenders, Bumpers, hood and doors all made out of Aluminum. This would all then be bolted and super Hi-tech glued to the main body, B pillars with roof which would be made out of Titanium and the rear quarters and Bumper out of cold roll steel. Of course this would all be tide together with a super stealthy chrome-moly Roll cage hidden inside. In other words, the weight increases in the direction of the rear of the car.
Talk about a CG Lightweight masterpiece. Talk about wishful thinking. LOL.