I don't know a lot about roller coasters, especially about their history. I do have a great web address for you which links to several good sites on the science and technology of roller coasters. These sites will give you a lot better information than I can.

http://dir.yahoo.com/Science/Physics/Mechanics/Amusement_Park_Ride_Physics/

See especially:
http://www.learner.org/exhibits/parkphysics/

Also for some history see:

http://coasters.eb.com/

Good luck!

Actually, there is a lot of information on the web about roller coasters- including buildable simulations. First the Web sites:

1) http://141.104.22.210/Anthology/Pav/Science/Physics/book/home.html
2) http://roller.coaster.net
3) Type http://www.yahoo.com and query: Roller-coaster

To answer your specific questions-- Early roller coasters were invariably built out of wood with steel rail tracks. This lead to a fun high-speed ride -- but the train could not be inverted.
I don't know about magnetic roller coasters -- all that I have seen rely on captured rails (i.e. the wheels surround both sides of the rail. Magnetism is used in the motors that drive a coaster -- typically, the coaster is in free-fall coast unless it must climb a large hill. Most commonly, there is a motor driver chain cogging assembly to lift the train up the hill -- where it 'coasts' back down....

Most of the modern coasters use polyurethane wheels to minimize noise and friction loss, and use rails made of cylinderical pipe which can be entrapped by the wheel system so the train cannot leave the tracks -- even if it is stopped upside-down. Also, several new designs use a single main track, to allow swinging action -- freeing up another degree of freedom.

You might try to build a simulation of a new super-roller coaster using the tools on the first web site -- maybe you'll design the roller coaster of the future...