In terms of a military role, the Hitler Youth contributed directly. The 12th SS Panzer Division Hitlerjugend was formed in February of 1943 from Hitler Youth members born in 1926. That meant that many of the boys were only seventeen and received candy in their rations instead of cigarettes! The enlisted members of the division had grown up under Nazi propaganda and had lived their entire cognizant lives knowing only the rule of Adolf Hitler.

As a result, morale was extremely high, and the division was as a result decimated in Normandy, attacking and defending viciously. After escaping, the division again fought in the Battle of the Bulge, and was then sent to fight the Soviets in Hungary. After the failed Operation Frühlingserwachen to take the Hungarian oil fields, it withdrew to Austria and surrendered to the Americans at war's end.

Another significant role the members of the Hitler Youth played was the Luftwaffenhelfer, bolstering the Luftwaffe's anti-aircraft defenses operating guns, searchlights and acoustic detectors. Anti-aircraft guns were unfortunately among the US 9th Air Force's favorite targets. Disturbingly, boys as young as those born in 1928 and 1929 were drafted into service to assist in the very last days of the war, including in the Battle of (and in) Berlin.

Sources:

The 12th SS: The History of the Hitler Youth Panzer Division volumes one and two, by Hubert Meyer