Completed and commissioned in April 1943, she served in World War II, operating in the Solomon Islands campaign, the New Guinea campaign — during which she sank the United States Navy destroyer USS Henley (DD-391) — and off the Admiralty Islands.

[1] For surface running, the boats were powered by two 500-brake-horsepower (373 kW) diesel engines, each driving one propeller shaft.

[4] Upon commissioning, Ro-108 was attached to the Sasebo Naval District and was assigned to the Kure Submarine Squadron for workups.

[4] She avoided detection and achieved an attack position, and at about 18:12 she fired four torpedoes at the destroyers, which presented overlapping targets.

[4] Henley′s crew abandoned ship, and at 18:29 she broke in half and sank by the stern at 07°40′S 148°06′E / 7.667°S 148.100°E / -7.667; 148.100 (USS Henley (DD-391)) with the loss of 15 lives.

[4] While heading back to Rabaul, she received orders on 26 October 1943 to patrol off Lae, New Guinea.

[4] After delivering her cargo at Sarmi on 21 November 1943, she patrolled off New Britain in the Arawe-Cape Merkus area before returning to Rabaul on 9 December 1943.

[4] Before reaching Sarmi, she was on the surface recharging her batteries in the Bismarck Sea northeast of Long Island at around 01:14 on 17 December 1943 when a PBY-5A Catalina flying boat of U.S. Navy Patrol Squadron 52 (VP-52) attacked her.

[4] The plane's crew reported seeing Ro-108 sinking by the stern and claimed to have sunk her[4] — some historians have credited the plane with sinking the submarine I-179, although I-179 had sunk in a diving accident off Japan in July 1943[4] — but Ro-108 survived the attack, albeit with serious damage that forced her to abandon her supply mission.

[4] After calling at Rabaul, she got back underway on 20 December 1943 bound for Japan, where she arrived at Sasebo on 1 January 1944 to undergo repairs.

[4] She again got underway from Truk on 12 April 1944, setting out on her fourth war patrol, this time south of the Admiralties.

[4][5] The picket line was tasked with providing warning of any move toward the Palau Islands by Allied invasion forces.

[4] England established sonar contact on her at 23:19 at a range of 1,650 yards (1,510 m) and Raby made an unsuccessful attack against Ro-108, which was at a depth of 250 feet (76 m) and making 2 to 3 knots (3.7 to 5.6 km/h; 2.3 to 3.5 mph) on a heading of 150 degrees true.