This Article Contains Spoilers -
WARNING: This article contains major spoilers. If you do not wish to know vital information on plot / character elements in a story, you may not wish to read beyond this warning: We hold no responsibility for any negative effects these facts may have on your enjoyment of said media should you continue. That is all.
Such a shame. Your wedding was the last thing I was living for. I lost a grandson, but you, you've lost the love of your young life. Poor child.
~ Rose to Betty (thinking she was Polly).
Roseanne "Rose" Blossom, mostly known as Nana Rose, is a supporting character in the CW Soap Opera Riverdale. She is the mother of Clifford and Claudius, the adoptive mother and mother-in law-of Penelope Blossom, and the grandmother of Cheryl and Jason Blossom. While she is portrayed as a protective and decent person throughout most of the series, it is revealed in the third season that she forced Penelope to marry her own adoptive brother, and it is heavily implied that she abused her as well. As a result, Penelope grew up to be cold, abusive, and manipulative.
In present day, Rose is shown to be a caring and decent person, despite having become delusional and senile due to her old age. She was willing to support Polly's relationship with Jason, and she genuinely cares about Cheryl and her well-being. However, it is revealed that she was once abusive and twisted. She abused Penelope to the point where she forced her to form a relationship with her adoptive brother, Clifford, resulting in a very unhappy marriage and also resulting in Penelope's villainy.
Rose is not a villain in this season, having given up on her abusive ways before the main plot took place. It is revealed through flashbacks that she gave Jason blessing to marry Polly. She also gave him her ring. Unfortunately, Jason is kidnapped and killed by his own father, and the ring is taken from him.
Rose is not a villain in this season either, and she cares for her granddaughter Cheryl as much as possible. At some point, Penelope and Claudius (Rose's long-lost son) decide to murder her. They shove her down a flight of stairs, but she survives. Later, when Cheryl is sent to the Sisters of Quiet Mercy, Rose informs Toni (Cheryl's girlfriend) about Cheryl's whereabouts and condition.
In this season, Rose has yet to appear onscreen in present day. However, it is revealed that she adopted Penelope many years ago. Unfortunately, she started abusing Penelope, and she went as far as forcing her to marry her own brother. As a result, Penelope turned out to be the way she is: a cold, manipulative, and abusive sociopath.