No, FPSC can't directly import the heightmaps.
However I do recommend a product, also sold by the game creators, called T.Ed:
http://www.thegamecreators.com/?f=ted
With T.Ed you can make landscapes (with the rolling hills you'd like). T.Ed can directly import heightmaps. From T.Ed you can export it as a .X file, then just look on the board for some info about putting that T.Ed file into FPSC.
EDIT: Note that you may seriously slow down the FPSC Engine depending on the complexity of the landscape you are trying to create. Don't make it a trillion polygons just so it looks smoother... you want to find the right comparison between looking smooth and functioning fast. For a simple hill I'd try to keep under 2000 polygons. Make the sure the object is static in FPSC so it doesn't try and overcalculate the things it can do.