Roof, 22, was convicted last month of 33 federal charges, including hate crimes resulting in death, in connection with the carnage at the historic Emanuel African Methodist Episcopal Church in downtown Charleston.
Jurors deliberated for less than three hours.
Roof, who represented himself for the penalty phase, was unrepentant during his closing argument earlier in the day.
He told jurors he still felt the massacre was something he had to do and did not ask that his life be spared.
Roof still faces a trial on murder charges in state court, where prosecutors also are seeking the death penalty.
To Receive Free News Updates , Add Us To Your WhatsApp: 08080810909; BBM Pin: D8CB58EE