The comedy, which was created by Sharon Horgan, stars Jenna Elfman as a woman whose children have been raised by her mother Marian.
Elfman's character Julia is forced to address her responsibilities when Marian decides it is time to live her own life.
According to Deadline, Conroy has now signed up for the role of Marian.
Conroy previously starred as Ruth in Six Feet Under. She has also appeared in Happy Town and has guest starred in episodes of Grey's Anatomy, Desperate Housewives and How I Met Your Mother.