Fire crews, police and ambulance were called to the scene.
Police were last night unsure what had caused the four-wheel-drive vehicle to roll.
A single lane was opened so traffic flow could resume.
The patient, a male in his 50s, was in a stable condition suffering moderate head injuries in the crash, St John Hawke's Bay district-operations manager Stephen Smith said.
The road has been a notorious black spot for car accidents in the past.
In February this year, five people were injured, one seriously, in a crash between a car and a logging truck near Te Pohue on the Napier-Taupo Rd.
The crash caused the road to be blocked in both directions for several hours.
Two months later, a 23-year-old man was found crashed near the Te Haroto summit on SH5.
His car was found stuck in a fence and had a flat tyre.
He had fallen down a bank and was entangled in blackberry bushes, which rescuers had to cut away to free him.
In January 2014, a van left the Napier-Taupo Rd on a moderate downhill bend about 6km north of Te Haroto. The van then plunged 10 metres down a steep bank.
A five-month-old baby was seriously injured in the crash.
A spokesman for the police District Command Centre is urging drivers to take caution on Hawke's Bay roads.
"There have been far too many incidences like this on our roads recently," he said.
"Drivers need to slow down, anticipate corners and be more road aware."
