The process is called ROLL-FORMING
A better process (better but much more expensive) is the extension of it called, PROGRESSIVE ROLL-FORMING. it’s better because it rolls the extrusion in stages, minimizing the stress, but also more expensive to orger 10 rolls than just 3. But the video i saw for bike rim was a 3-rolls roller. (i’m guessing the progressive roller is more efficient with a continuous supply, making it hard to roll into circles without it rolling onto itself.)
http://www.advantagefabricatedmetals.com/roll-forming-process.html
Another important thing: The part should be cooled. It’ll then be COLD ROLLed (cold formed) therefore pressing particles closer together, in the same direction. resulting in much stronger parts. (kinda like forging)