In what way do you mean rough? As in roughly made (e.g. track with no ballast and cheaply main, and laid, sleepers with light weight rails), or as in track that is rough to ride on (poorly maintained, as well as the result of the first option).
The first option, well it's been done by some people. Someone even made the sleepers on their own as well, so you can place your choice of rails over them.
For the second option, it is up to you. No matter how rough looking I make the mesh, the train will still only go in a straight line. What you can do instead is add a number of spline points a short distance apart, raise them up and down by a few centimeters (I actually make them about 0.1m height difference), as well as move them around a little bit. Remember, small amounts, otherwise trains won't track over them properly.
Zec