Go ask this at /r/rollercoasters. Several folks over there are very well versed in the processes involved in coaster track fabrication. Processes are different between different kinds of rides. Most are a rolled tube setup, some are wood and others are made entirely of flat plate.
There’s a few videos online, but manufacturers tend to be pretty secretive of the exact machines and techniques that they use. Most tubular steel rides share a similar technique that requires bending of the tubes slowly in various dies and in various specialized pipe benders. Everyone has their own take on it, bit most of the magic is in rolling the pipe as accurately as possible.
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