remote sensing - Extracting roads out of Landsat raster images

For a study into the expansion of road networks in the rainforest I am trying to extract roads out of Landsat images. We already have sharp and cloud-free composites on which the roads are clearly visible by eye but extracting those into line features is proving difficult so i was wondering if anyone knows a good algorithm or method that can handle the large images that Landsat provides? I've tried Grass's r.thin but this doesn't seem to work.