What are these tiny kidney bean sized things in my rotisserie chicken
Your chicken was a rooster and what you found are his testicles. If you are not queasy, this forum entry gives you a picture and some more anatomical details.

While animal testicles are typically edible and often a speciality/delicacy, many westerners are not necessarily familiar with them, especially in animals as comparatively small as roosters. Asian (e.g. Chinese) cuisine knows various dishes based on chicken testicles, and there‘s also a Hungarian dish that’s basically a stew/goulash. 

On the other hand, they have confused unwitting consumers as readily reported by the kind of media that favors sensationalism.

So don’t worry, you can simply eat them, if you want. Or get inspired by Heston Blumenthal’s Regency recipe for his Fairytale Feast.