Rangers dont need roll bars. I rolled my 06 off of an onramp and it held together great :P , only a little crumpling on the drivers side. And now I have a 07.
I found this site along my searches for lightbars and they make roll bars too. I emailed a little bit with them back and forth and they have great customer service and will custom fit if you ship them the dimensions.
It looks like it can be a little pricey but I imagine as it is with myself, better off paying a little more and getting a quality product especially with rollbars.