It all depends.
Depends on the gear in the back, it depends if the ranger has a cab system on it (more topheavy) and it depends on if you have a run at the hill or not. Heck, it even depends alot on weather the hill is smooth or rough surface.
Never actually checked the angle of attack, but have been on some that I will never go up again. I had to put weight on the front to keep it down so I could get out.
You will get a good feel for what your ranger will and won't do as you get so more time in it. and especially when it's new, it's a good idea to do everything possible to keep the shiny side up.
Polaris says no more than 15 degrees. I'd say they're good for at least 30-40 myself. but then again, I spend alot of time on 2 wheels.