Do they go round cooking the roast? (5)
I believe the answer is:
rotas
'do they go' is the definition.
Although both the answer and 'do' are nouns, they are not in the same form of the noun.
'cooking the roast?' is the wordplay.
'cooking' indicates an anagram (letters cooked up into a new form).
'roast' is an anagram of 'ROTAS'.
'round' is the link.
Can you help me to learn more?
(Other definitions for rotas that I've seen before include "Rolls" , "Rosters" , "Cycles of duty" , "Duty lists" , "they tell us when to work" .)