Assassination at Winterfell

"Maester Wolkan, send ravens to all the Northern Houses, Roose Bolton is dead, poisoned by our enemies."

- Ramsay Bolton after murdering his father.

The Assassination of Roose and Walda Bolton is an event during the War of the Five Kings, in which Roose Bolton, the Lord of Winterfell and Warden of the North, is betrayed and murdered by his own son, Ramsay Bolton.

Prelude
After having defeated the forces of Stannis Baratheon, the Boltons celebrate a hollow victory, as Sansa Stark escapes during the chaos of the battle with help from Theon Greyjoy. With the birth of Roose Bolton's child looming, Ramsay's position as heir becomes more uncertain, especially when Roose subtly hints that he will disinherit Ramsay in favor of the baby if Sansa cannot be located.

Events
"You will always be my firstborn."

- Roose Boltons' final words before he is killed by Ramsay.

During a meeting with Lord Harald Karstark about future plans for the North, Ramsay suggests they storm Castle Black as Sansa has probably fled there to find safety with her brother, Jon Snow. Roose immediately shoots down the proposal, saying that killing the Lord Commander of an ancient order like the Night's Watch will rally the North against them, chastising Ramsay for being a wild dog. They are then informed by the Boltons' Maester that Walda Bolton has given birth to a boy. Ramsay proceeds to congratulate Roose and hug him, while discreetly feeling for chain mail on his back. When he finds none, Ramsay stabs Roose in the chest. Mortally injured, Roose collapses to the floor and dies, ironically in exactly the same manner as when he killed Robb Stark. Ramsay then instructs the Maester to send ravens out with the message that Roose was poisoned by his enemies, when the Maester hesitates, Harald reminds him that Ramsay is his Lord now. Ramsay is quick to solidify his position as Lord Bolton, luring his stepmother and newborn brother to the kennels, where he feeds them to the hounds.

Aftermath
With the deaths of Roose and Walda, Ramsay is now the only living member of House Bolton and the new Lord of Winterfell and Warden of the North. However, his actions will most likely earn him the ire of House Frey, adding to what was a precarious position to begin with between the threat posed by Jon Snow and Littlefinger earlier informing against the Boltons to Cersei Lannister of Sansa's whereabouts.

In the books
As of the current point the books have reached, Roose and the pregnant Walda are still alive, though their deaths in "Home" implies that they will die in The Winds of Winter.