Carwyn ap Myrddin and Kelvin Davies crossed before half-time to send RGC in at the break with an 11 point lead.
Richard Hopkins dived over in the corner and full-back Llywarch ap Myrddin forced his way over from close range as Chris Horsman's side pulled clear in the second half.
And they put the icing on the cake with a penalty try from the last play of the game as the RGC forwards took apart their opponents at a scrum.
After six successive away games, RGC's first home game of the season was a huge success both on and off the pitch.
"It was a fabulous day and I was told if you held a league game in north Wales then the people would come and they certainly did," said RGC 1404 General Manager Rupert Moon.
"Lots of people came from far and wide and we had a lot of travelling support. The north Wales supporter is a unique animal and they are desperate to see rugby shown there. They got that on Saturday and showed their support.
"We've had six straight away games with 60 hours spent on the coach and it was great to play a home game at Eirias Park. We're looking forward to our next home game now which is on November 17.
"I'd like to say a big thank you to all the volunteers and juniors who came from all over north Wales. We had a mini festival before the match and at half-time which was great to see the next generation of young talent coming through.
"We're lucky we've got such a fabulous facility."
The win over Rumney sent RGC back into second place, just five points behind leaders Ystrad Rhondda with a game in hand. And although head coach Chris Horsman believes there is more to come from his side, the former Wales prop was delighted with how the day turned out.
"We got the bonus point try and then got the fifth with the last play of the game and the evening was successful in terms of getting 1,600 people through the gates - the support we had was absolutely fantastic," he said.
"To think we almost got 2,000 speaks volumes of where we are and I can't thank the people enough."