The term 'rule the roost' is an idiom that means to be in charge or to have authority over a certain situation. The two crossword solutions for this term are 'REIGN' and 'DOMINATE', both of which imply having control or power. REIGN is a verb meaning to exercise royal authority, while DOMINATE is a verb meaning to have control or influence over something. Together, these two words accurately describe the meaning of the phrase 'rule the roost'.