Any of the Stratosphere chips that have the tower on them have a roller coaster. It's probably very tiny, but it's there.

Several of the Holiday Inn Boardwalk chips from Vegas have a roller coaster on them. I'd also look closely at the NY NY chips if any of them show the outside of the casino it is a good chance you'll find a coaster there.

There is another casino in Nevada, not in Vegas though, that has a big coaster also. I can't remember where, but someone here will know. They might have pictured a coaster on their chips at some point.

Greg