"Rule the roost" is an idiom that refers to having control or dominance over a situation or group of people. There are several synonyms that can be used in place of this expression, such as "call the shots," "run the show," "be in charge," "have the upper hand," "hold sway," "be the boss," or "be at the helm." All of these phrases imply a sense of authority and leadership, and can be used in different contexts to convey the same message. Whether in a professional or personal setting, it's always important to have a clear understanding of who's in charge and who's calling the shots.