Cooks in an oven (5)
(Other definitions for bakes that I've seen before include "Gets hot" , "Cooks in oven" .)
'cooks in an oven' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for roasts that I've seen before include "traditional Sunday food" , "Cooks meat in oven" , "Cooks in dry heat" , "Has a go at" , "gets very hot" .)