NEW ORLEANS — Over the past century, Alexandria-based RoyOMartin has grown from a single sawmill founded in 1923 by the company’s eponymous founder to the largest private forestry and timber products business in Louisiana. …Now, after six years at the helm of the company founded by his grandfather, third-generation CEO Roy O. Martin III, 65, is passing the torch to President and Chief Operating Officer E. Scott Poole, the first chief executive to lead the company who is not a member of the Martin family. …The transition comes at a time of upheaval in the timber industry. …The company has its corporate headquarters in Alexandria, a plywood and timber mill in Chopin, a plant in Oakdale that specializes in manufacturing a type of engineered wood called oriented strand board or OSB, and a facility in Corrigan, Texas, that also makes the engineered wood products.