The home side wasted little time kicking ahead after the break.
Halfback Matt Golding sniped around the corner of a ruck and then kicked the sideline conversion to make it 15-3, before stepping up to slot a sweetly struck penalty from more than 40 metres out.
A sustained period of Rotoiti pressure, typified by numerous forward thrusts around the fringes, culminated in a short range unconverted effort to Jacob Marsters, making it 18-8 after 54 minutes.
The arm wrestle continued, with Mount midfielder Teddy Stanaway, especially, not shying away from the physical stuff.
Down 10 points with as many minutes to go, Rotoiti turned down repeated kickable penalties inside the Mount's 22, instead opting for lineout drives.
When Royal finally barged over in the right-hand corner there were just three minutes remaining, leaving the visitors to travel the length of the field in search of a try following Ripia's wayward conversion attempt.
Miscommunication following a quick tap decided the match, allowing Bardoul to again storm up field before backing up his effort to crash over in the corner.
Elsewhere, the big guns mostly fired on the back-end of a big Queen's Birthday weekend of Bayfair Baywide premier club rugby competition.
Tauranga Sports bounced back with a 35-20 win over Te Puna, while Te Puke outlasted Rangataua 22-17.
Rangiuru won their first match of the season 25-24 over Greerton Marist, with Whakarewarewa cashing in their five competition points due to their pre-season 48-0 thumping of Opotiki.
Mount Maunganui, Te Puke, Greerton Marist and Tauranga Sports claimed the points in the development competition.
