"So many of those jeeps don't have any roll bar. When where roll bars standard equipment?"
This is always an interesting question. Most definitely, roll bars were never a factory manufacturer (Willys or KaiserWillys) option with one exception: the early Renegade I models from around 1969-1971 came with a roll bar from factory. Before that, roll bars were an aftermarket supply, or as was the case with many 'options' from those days, they were dealer supplied from aftermarket suppliers and added on by individual dealers before sale to the public (or added on as part of a sale). There was a lot more individuality from dealers in those days as opposed to today when almost all dealers across the country have the exact same 'factory' or manufacturer options. Many early jeeps came with dealer installed PTO winches - none of the winches were actually installed at the jeep factory but at individual dealerships. Same for hardtops from before 1976 as well. Thus all the different variations of parts and pieces and accessories available for early jeeps.
When AMC took over for the 1972 model year, roll bars became much more common. Whether they were standard on all CJ at that time, or just a common factory or dealer option I am not 100% sure. I think they become a factory option at that point, but I believe a base model CJ would still have been without a roll bar. I believe the roll bar became standard factory equipment on all CJs in 1976 - when AMC did a pretty big redesign to the CJ line including introducing the CJ7.