The away side put on a much improved performance after the break with Zac Hohneck diving over but as in previous weeks Rotoiti's kicking let them down with Logan Henry this time missing four penalties and a conversion.
Rotoiti coach Dave McLean said it was a "game of two halves" and was disappointed his team didn't move into second gear towards the end of the closely contested match.
"The conditions were awful and we let Tauranga into the game but it was the missed kicks that really cost us," he said.
"They had a tough forward pack that we couldn't breach and even though we put in a great defensive backline they got away from us."
The result sees Rotoiti fall to sixth in the table on six points.
Leaders Mount Maunganui Sports won a war of attrition against Te Puke Sports 17-13 at Blake Park whilst Greerton Marist sneaked past Whakatane Marist 18-17 in a deserved away win.
But Rangataua Sports proved the exception to those close margins with a 24-0 bonus point win at Te Ariki Park over in-form Te Puna.
Meanwhile in Premier 2, top of the table Whakarewarewa were the only local team to record a win - beating fellow former Premier 1 side Arataki 67-12 with an impressive performance.
Whakarewarewa coach Kopae Irihei said he was "delighted" with the result and the side greatly benefited from the return of player Kelly Haimona from playing over in Italy.
"Arataki are one of the harder teams in this division so it was very pleasing to see us win in such a stylish and empathic manner," he said.
"Everybody played well, and forwards and backs really clicked and that is why we got over the line so many times.
"We were very impressive in the lineout - we stole so many of their balls and scored a lot of tries off the back of that.
"It was great to see Kelly back with us, because he added some great quality on the day."
Whilst Marist St Michael's suffered a 33-5 away loss against Opotiki and Waikite went down 19-0 away to Paroa.
Ngongotaha had the closest defeat - losing admirably 13-7 away against Poroporo, leaving them bottom of the table with just one point.
Additional reporting from Peter White.
Results and standings:
Baywide Premier 1 Results:
Tauranga Sports 12 Rotoiti 5, Greerton Marist 18 Whakatane Marist 17, Rangataua 24 Te Puna 0, Mount Maunganui 17 Te Puke Sports 13.
Baywide Premier 2 Results:
Whakarewarewa 67 Arataki 21, Paroa 19 Waikite 0, Opotiki 33 Marist St Michael's 5, Poroporo 13 Ngongotaha 7.
Baywide Premier 1 Points:
Mount Maunganui Sports 14, Te Puna 9, Rangataua 9, Tauranga Sports 8, Te Puke Sports 7, Rotoiti 6, Greerton Marist 5, Whakatane Marist 4.
Baywide Premier 2 Points:
Whakarewarewa 15, Paroa 13, Poroporo 10, Opotiki 8, Arataki 6, Marist St Michael's 4, Waikite 2, Ngongotaha 1.