"Go one's rocker" is a colloquial phrase used to describe someone who has lost their mind or has become insane. However, there are several synonyms that can be used to express the same sentiment. Some of these terms include "lose one's marbles," "lose one's mind," "have a screw loose," "go nuts," "go bonkers," "go crazy," and "go off the deep end." These phrases are often used humorously and colloquially to describe someone who is acting unusually or irrationally. It is important to remember that mental illness is a serious issue, and these phrases should be used with caution and sensitivity.