A couple about the HF tubing roller.
I've also used pipe within pipes to make flat rollers too.
https://talk.newagtalk.com/forums/thread-view.asp?tid=939333
Initial post
https://talk.newagtalk.com/forums/thread-view.asp?tid=714384
Edit:
Swag Off Road makes a lot of dies for forming various materials as well. Their dies work in the HF tubing roller too.