Roku delivers its content via an Internet connection. The side of the box should say that an Internet connection is required.
The Express only connects to your network via WiFi, so if your Internet setup must include WiFi.
Roku has a video on this page that might help with setup: https://www.roku.com/products/roku-express
You can use your phone's hotspot, but what most providers don't tell you is that after a certain bit of usage, they'll throttle your service. That is, after around 20-22 GB data use, they don't cut you off (unlimited) but they will cut your speed. That might make using your hotspot a less than optimal experience.
So can I use the roku without WiFi if I purchase the channels ?
Roku requires an Internet connection to stream. The Express connects via WiFi only.
No one has explained it and I can’t get hold of anyone to ask.
would you be so kind as to run through how I set it up on my hotspot I have unlimited data
Just a reminder: this is a bad idea. Unlimited data will be throttled after 20+ GB usage and it will be unwatchable. You have been served notice twice. If you still want to proceed, okay. It's on you.
Depending on your phone, there can be different ways of turning on a hotspot. I have an iPhone, so I can tell you you go to Settings > Personal Hotspot > Allow Others To Join [ON]
You'll see your password in the Wi-Fi Password section. That's what your Roku will need to seek. Once you have your hotspot on, then power up your Roku. It will walk you through the setup, to include network connection.
Just repeating above that most cell providers don't really have "unlimited data" in the way most people assume. (And it is often limited even sooner on the hotspot because they know you are far more likely to reach it there.)
That said: On Android, Settings->Network & Internet -> Hotspot & Tethering->Set up Wi-Fi hotspot.