He died whilst commanding it in its last stand during the sack of Rome in 1527.

He married Anna Meyer of Knonau in 1500, and later Elisabeth Klingler, likely in 1517.

Politically, the years of the service of Kaspar Röist were among the hardest, particularly in the diplomatic tensions between the Holy See and the Holy Roman Empire in 1527 which resulted in the sack of Rome, perpetrated by Landsknechts, Spanish, and Italian mercenaries in the pay of the Emperor Charles V who was determined to reassert their supremacy over the Church of the Empire.

During the assault on Rome, Kaspar Röist had fortified himself at the head of the 189 recruits in the Teutonic Cemetery, around the central obelisk in the cemetery desperately trying to resist but to no avail, covering the flight of Pope Clement VII to Castel Sant'Angelo.

Röist was wounded during this battle and later sought refuge in his house, but was followed by the troops, who killed him in front of his wife.