An open and exciting first half sparked to life in the 12th minute, with Shaun Leonard putting Emlyn in front with the first penalty of the game.
However, just a minute after and almost straight from the kick off Rhondda hit back with a try, David Gratton running down the right wing to touch down in the corner and give Ystrad a 5-3 lead.
With four minutes of the first half left, Emlyn seized control after a brilliant cross field kick fell to Dan Davies, who rode a challenge to give his side a 8-5 half time lead.
A Shaun Leonard penalty shortly after the break stretched their lead further, before Rhondda clicked in to gear with a devastating second half performance.
A neat chip put Emlyn on the back foot, and a turn over from the resulting pressure saw Chris Clayton cross the line, the conversion was then slotted home by Rhys Truelove to give Rhondda a 12-11 lead.
Two Emlyn penalties then restored their lead, but pressure from the Rhondda pack pushed them over for a try and ten minutes before the end Truelove added another penalty to put the game beyond the reach of a spirited Emlyn.
