I like roller coasters but I'd never do this

It's an actual roller coaster. It normally has actual roller coaster cars on it. This was done for a stunt. They made special skates to use on the roller coaster track:
http://metro.co.uk/2009/07/21/speed-freak-rides-a-860m-rollercoaster-on-rollerskates-286155/

I believe it's how they test them before putting them is service, not positive on that though.

Nope, it was for a stunt. Read the article linked above.

I wanna come for some fun and donuts :(

Always make room for lucifer on a road trip *opens box of doughnuts* "doughnut?"

YES! Fuck yes gimme