National Forest Roadless Area Conservation Act - Identifies roadless areas within the National Forest System set forth in specified maps as National Forest Inventoried Roadless Areas, and directs the Secretary of Agriculture to manage such Areas to maintain their roadless character. Authorizes the Forest Service to modify such maps for the sole purpose of improving their accuracy or inclusiveness. Requires any substantial modification of those maps to be made through the national forest management planning process and documented in an environmental impact statement.