Commissioned on June 17, 1941, at Montreal, Rosthern arrived at Halifax on June 26. She joined Newfoundland Command and left St. John's for Iceland on October 7 as ocean escort to convoy SC.48. She proceeded on to the Clyde, where mechanical defects kept her for two months, and arrived at Halifax on December 28 for further repairs, not resuming service until mid-February, 1942. She left Argentia, Nfld., on February 27 with HX.177 for Londonderry, and was thereafter employed continuously on North Atlantic convoys until June, 1944. In April, 1942 she became a member of EG A-3, re-numbered C-5 in May. Rosthern took part in three major convoy battles: SC.100 (September, 1942); ON.166 (February, 1943); and SC.121 (March, 1943). She left Londonderry for the last time on May 27, 1944, and on her return to Canada became a training ship at Halifax for navigation and ship-handling, attached at first to WLEF and then, from December onward, to Halifax Force. She carried out workups at Bermuda in December, escorting HMCS Provider on the homeward trip. Rosthern had no long refits during the war, and never did have her fo'c's'le lengthened. Paid off on July 19, 1945, at Sorel, she was broken up at Hamilton in 1946.
Focsle Extension Never Done.