'To rule the roast' definitions:

Definition of 'To rule the roast'

From: GCIDE

Roast \Roast\, n. That which is roasted; a piece of meat which has been roasted, or is suitable for being roasted. [1913 Webster]
A fat swan loved he best of any roost [roast]. --Chaucer. [1913 Webster]
To rule the roast, to be at the head of affairs. "The new-made duke that rules the roast." --Shak. [1913 Webster]