表达 “rule the roost” 相当于汉语里说的 “当家作主”，指 “在一群人或一家人当中最有权威和影响力、可以作决定的那个人”；这个人通常要作出所有重要的决定。

• His girlfriend rules the roost, so he’ll have to check it’s OK with her first．
  他的女朋友平时作主，所以他得先和她确认一下这件事。
• My mum is always in charge of important decisions. She rules the roost.
  一直以来，我妈妈负责作重要的决定。家里她作主。
• I always thought Dave ruled the roost in his house, but I think his dog is really in control!
  我一直以为戴夫是他家作主的那个人，但我看他的狗才是真正管事的！