It's easy to do on your own. Classic buffalo sauce is just Frank's Red Hot and butter. Dip the parts of your rotisserie bird as you remove them for the best texture.
I have seen premade buffalo roast chicken at the deli plenty of times. But that's more uniform for slicing onto sandwiches, not the same as rotisserie meat.
Franks is a classic but anyone I know makes better buffalo sauce using Crystal hot sauce and butter. It's a bit less acidic. That deli counter buffalo roast chicken is weirdly good also.
A rotisserie chicken just coated in buffalo sauce would be pretty bad. It works for wings, because the meat to sauce ratio is good. Other parts of the chicken don't work as well just being coated in sauce.
Maybe it's too messy to sauce it while on the rotisserie? Or it makes it gross if you marinate it in buffalo sauce due to the acidity and how long it cooks?
Hmm, i have no idea what is buffalo sauce so i googled it, it sounds like a good coating for roasted chicken, like Ayam Percik, a Malaysian cuisine which they coat the chicken with the sauce and roast it, then coat it again before serving.
I want to try the funny Zuck sauce but I live in the UK so they'd have to re-do their tagline. Over here it'd be pronounced "the source is the boss", which is just weird.