At 21.35 hours on 21 Feb 1943, U-664 fired torpedoes at convoy ONS-167 about 550 miles west of Fastnet, Ireland and reported three hits on a steamer and one on a tanker. The ships hit were Rosario in station #11 and H.H. Rogers in station #13.

The Rosario (Master Gustav J.A. Larsen) was hit by two torpedoes on the starboard side. The first hit at the #2 hold and the second at the #5 hold. The explosions blew off both hatch covers and threw sand and slag into the air. The engines were stopped immediately because the ship developed a 35° list and eventually listed to 45°. The eight officers, 36 crewmen and 19 armed guards (the ship was armed with one 5in, five 20mm and two .30cal guns) began to abandon ship in great confusion because the heavy list prevented the launching of boats and rafts. The ship capsized and sank within three minutes. The survivors had to jump overboard and swam to one raft and two floats that floated free. Several men swimming in the water were picked up after about one hour by a lifeboat from H.H. Rogers. One officer, 13 crewmen and 16 armed guards were picked up three hours after the sinking by the British rescue ship Rathlin and landed at Halifax on 6 March.