As Roulston was taken by ambulance to Southland Hospital for tests, news the race lead was up for grabs filtered through the peloton and teams scrambled to adjust their tactics.
Ultimately, a commanding performance saw PowerNet's 19-year-old weapon Josh Atkins ride his way into the race's history books as one of the youngest to claim a stage victory.
Atkins surged into the lead at the start of the daunting Crown Range climb and muscled his way to the finish line to claim the PowerNet team's inaugural stage win.
"It's good to finally get a stage win for PowerNet ... that's all we wanted so we got that and I got the yellow," he said.
"I didn't really come into the Tour with too many goals. It was a last-minute decision and for a while I was regretting coming down."
The climb wasn't without its unexpected challenges.
"I got ridden into the back of the wheel so my derailer was pretty banged up so I was riding the whole climb with my gears chopping and changing. The Tour is never without drama."
Atkins now has a 1min 9sec lead over Ascot Park Hotel's Patrick Bevan, of Rotorua, with Kia Motors' George Bennett, of Nelson, a further 16sec back. The trio also hold the top three placings in the battle for the Under-23 jersey.
Auckland's Gordon McCauley extended his dominance of the Sprint Ace jersey to 63 points over Share the Road's Chris Macic, while Dunedin's Joe Chapman retains the King of the Mountain jersey for a fourth consecutive day with a 32-point advantage over Brendon Sharratt, of Wanganui.