The phrase "distinct roles" means that different people or things have specific and separate responsibilities or functions. Each role is unique and serves a specific purpose. Full definition
He turned it from a 30 - man Royal Rumble into a 22 - player sport with distinct roles for distinct types of athletes, coining many of the position names we still use. (sbnation.com)
These crystals are composed of homologous molecules, BinA and BinB, which play distinct roles in the multi-step intoxication process, transforming from harmless, robust crystals, to soluble protoxin heterodimers, to internalized mature toxin, and finally to toxic oligomeric pores. (bioxfel.org)