Martin Marietta Materials Inc., the nation's second-largest producer of road-building materials, agreed yesterday to buy the Redland Stone Products Company for $272 million from Lafarge S.A. of France. Redland, the largest producer of road-building material in Texas, is expected to have 1998 sales of about $140 million. Martin Marietta Materials expects to operate Redland as a division based in San Antonio. Martin Marietta Materials, which is based in Raleigh, N.C., was spun off from the former Martin Marietta Corporation.