this minecart track with house is still in "beta" but it will be done as soon as possible, check out how far it already is, download the world save (its free)
oh yeah, on the mountain is a little brick hut with torches, which is the start of the rollercoaster, you should have a minecart in your hand or inventory

Its done, and now i've saved in such a way that you will immediatly spawn in the brick hut with a minecart in your hand, have fun