David Hearn matched Rocha's 64 to move into a tie for second place at 11-under-par 205. He is joined there by Brad Fritsch (68) and second-round leader Brad Sutterfield (71). Eddie Maunder and Doug McGuigan share fifth place at 9-under-par 207.
Rocha, a native of Brazil, opened with a birdie on the par-5 second, but tripped to a bogey at the fourth. He came right back with a birdie at the next.
The 26-year-old then dropped in back-to-back birdies from the eighth to get to seven-under. Around the turn, he birdied the par-5 11th and par-3 14th.
Rocha, who is looking for his first Canadian Tour win, then eagled the par-5 15th to move to 11 under. He closed his round with a birdie at the par-4 17th at Gorge Vale Golf Club to match the course record that Hearn had set moments before.
'Some days, you just get on a roll and nothing is going to stop you,' said Rocha. 'When it's your day, it's your day. You can't seem to do anything wrong. Today, I played the same as I did through the first two rounds without the double-bogey. In the end, I just scored a lot better.'
Hearn ran off four birdies over a five-hole stretch from the fourth to jump to 7-under. On the back nine, he picked up an eagle and two more birdies to set the new course mark.
'I'm just going to have to play steady and not worry about what anyone else is doing,' Hearn said. 'I feel I'm ready to win out here, and I'm confident in my game. Whether it happens tomorrow remains to be seen.'
Connor Robbins, Steve Scott, Mario Tiziani and Clint Jensen share seventh place at 8-under-par 208. Scotty Kral, amateur James Lepp, Craig Kanada, Craig Taylor and Jason Allred are one stroke further back at minus-7.