D.Roof murdered so many people during his mass killing spree that he certainly deserves execution more than anyone else presently, similar to Timothy McVeigh.
Note that Tim McVeigh repeatedly
demanded the death penalty. In his final manifesto in which he declared it was his
right to die for the gravity of his offense and he did not wish to enable a "corrupt, lying government" to torment him with "decades of confinement in one of their psychological torture pits."
Further note that McVeigh's execution took place in a
record short time from the day of sentencing. It is believed by many, myself included, that his death was expedited to shut him up. Because Timothy McVeigh's condemnations of the Waco Massacre, which was his primary motivation for the OKC bombing, had a strongly discomfiting effect on Bill Clinton, Janet Reno, BATF and FBI/HRT.
What McVeigh did was wrong -- but his reason was right. The same cannot be said for Dylan Root. What Root did, along with his reason, were as wrong as it gets.