Apple TV needs no other Apple products to stream but it helps to have an iTunes account and the Apple products, Mac, iPad, iPhone makes for more and enhanced use. You just need an Internet connection same as Roku and any other streaming device. Since I have always had an iTunes account I don't actually know if Netflix and Hulu+ can be watched without it since you pay those companies separately. I believe you can stream YouTube on Apple TV but not Roku. That alone gives you a lot of free, interesting and time consuming viewing.
I don't think I have ever been in a campground that gives you any kind of reliable streaming to use Apple TV or Roku type devices. What I do on the road is stock up on rental iTunes movies on my iPad and play them through an Apple cable hooked up to the TV. Once rented you have 30 days in which to watch them. Once you start watching a movie in that 30 days it is good for 24 hours before going "poof". So, rather than stream, just download when you have a reliable and very fast wifi connection. If I think I might watch a movie over and over, such as movies for the grandkids, then I buy them to play anytime. At home I can use AirPlay wirelessly from the iPad or computer to the Apple TV.