Following the Japanese Attack on Pearl Harbor, Rosecrans was transferred to 5th Marine Regiment located in New River, North Carolina, in March 1942 and succeeded Lieutenant Colonel William J. Whaling as commanding officer of 2nd Battalion on March 28.
Upon his recovery, Rosecrans was promoted to the rank of colonel and appointed quartermaster of I Marine Amphibious Corps under Major General Clayton Barney Vogel for a brief period before he was ordered to take command of newly activated 17th Marine Regiment (Engineer) on January 21, 1943 [REF].