Just try a car out with one fitted before you take the plunge. I was keen to get one for my 4/4 but having sat in one fitted with a factory bar I found my head was very close to it. I’m only 5’ 8”.
A very good point - also consider the need to use a 4 or 5-point harness and a helmet. In an accident even without a rollover, a conventional 3-point safety belt isn't going to be able to keep you securely in place and there's potential for some pretty nasty head injuries should you contact the roll bar.
Personally, I don't believe that (outside competition/track days of course) the risk of rolling is high enough to warrant having a roll bar. My strategy of avoiding crashing in the first place seems to have worked fine for the last 20 years
