A Benton, Wisconsin man was involved in a semi rollover south of Baraboo Friday morning.  Sauk County authorities said about 2 am, 45-year old Brian Mook was operating a Sysco Company double-bottom semi tractor unit south on Highway 12 near Groth Road in the Town of Sumptor when he lost control.  The semi rolled and came to rest across the median, blocking both the north and south bound passing lanes of Highway 12 for nearly 4-hours.  Mook was transported to Saint Clare Hospital in Baraboo for treatment of his injuries.  He was wearing his seat-belt.  Mook was cited for driving too fast for conditions.