Bandboy (also expressed as band boy) is a bygone term for a job similar to for what now is known as a "roadie." They set up, tear down, and maintain equipment, and music. They help-out backstage, making sure there are towels, drinks, ice.
Unlike a roadie, the bandboy was more like a personal assistant, or au pair, or butler/dresser for the leader — making sure suits were dry cleaned, shoes shined, and the like. On foreign tours a local "bandboy" would translate, find places to eat, change money, buy train tickets, and so on. Often the "bandboy" would disseminate information for the leader, hand out itineraries, room lists, and set lists. The role of bandboy was different with every band and had different duties than the more senior road manager, who dealt with promoters, booking agents, contracts, payroll, catering, and such. When times got tough, financially, road managers often performed bandboy duties — or band members themselves handled the bandboy duties.