[ 'rɒstə , 'rəʊst- ]
■ noun a list or plan showing turns of duty or leave for individuals or groups in an organization.
↘a list of names, in particular of sports players available for team selection.
■ verb chiefly Brit. assign according to a duty ~.
Origin
C18: from Du. rooster 'list', earlier 'gridiron', with ref. to its parallel lines.