A theme park outside Roanoke would be a decent idea. Who said investors wouldn't be willing to jump on it? The economy is booming in many ways, but consumer tourism isn't too huge. BUT... Americans still travel A LOT even with rising gas prices. Outside of Roanoke is a good location. It would suck up all of western VA, some of the south, central, and maybe even some further east. It would have to be something great to get tourism outside that. And it wouldn't hurt that it would be around colleges: VA western, Roanoke college, VA Tech, JMU, and UVA.

Back to the original question. While an amusement park usually draws pretty good dough and a good few people, it won't do wonders for the local economy. Other than supplying a few jobs... Amusement parks don't bring people for weeks. The local economy flurishes when something keeps you there. A park would only attract people for a day at a time, maybe 2. Even a hotel wouldn't be a huge success.

This is all based on the assumption that the amusement park isn't some amazing special park with some out-of-this-world rides.