I've had at least 5 dreams with roller coasters. Sometimes I'm riding on them, sometimes strangers are riding on them, and one time Bradley Cooper was. But I think the following dream was the one in which the presence of a roller coaster made the least amount of sense.
For some reason, I was Bilbo Baggins. Young Bilbo, too, and this is before The Hobbit movies existed, so it was my own interpretation of him. I've had very few dreams in which I wasn't myself, so to be Bilbo of all people was pretty strange on its own.
Anyway, a bunch of other hobbits and I were seeking a relic in an old Mayan-esque temple. I don't know what made them so adventurous. The temple was huge, put together with light brown stones and overgrown with emerald-colored vines. I don't know what relic we were looking for, and I'm not even sure if we ever found it. I just know that I was really excited when I found the exit at the other end of the temple.
I yelled to the others that I had found the way out, and they all began to follow me outside. There was a path of stones to follow, but the stones were fairly spaced out, and for some reason I knew that we weren't supposed to touch the green grass in between the steps. It was an arduous process, but we finally made it to the other end of the stepping stones. Then there was a sudden high-pitched screech that pierced the air. We all thought that it was surely a Nazgul.
But as we moved closer (why you would want to get closer to a thing like that, I haven't the slightest idea), and the corner of the temple was no longer obscuring our view, where we expected to find a Witch-king atop a fell beast, we found...
A bright yellow roller coaster on the horizon. The scream had been from the people on the coaster, not an undead ruler. It made too much sense to make sense, and I woke up accordingly.