I visited this place in May as part of a tour of Mid-west zoos. What struck me as a visitor from the UK was that Rolling Hills had an almost 'British zoo' feel to it (a bit like Marwell, for those who know that zoo), with fenced enclosures and functional exhibits - rather than multi-million$$$ immersion exhibits.
The animal collection is dominated by larger mammals, including an Indian Rhino, White Rhinos, giraffes (mixed with Grant's Gazelles), Pronghorn and quite a few big cats. There is also a small Reptile House and a Natural History Museum on the site. Definitely worth a visit if you're in the general area.