A first half goal from teenage corner-forward Mark Kavanagh was the turning point, as it helped Rathdowney-Errill into a six point lead (1-10 to 0-7) at the break.
The winners stormed out on the restart with points from Tadgh Dowling and Ross King (free). King finished with 0-10 and Kavanagh with 1-5 as the 2013 champions had no answer to a powerful display from Rathdowney-Errill, who face the Dublin champions in the provincial series.
Scorers for Rathdowney-Errill: R King 0-10 (7f), M Kavanagh 1-5, J Ryan, P Meehan, J Purcell, T Dowling, E Meagher 0-1 each
Scorers for Camross: Z Keenan 0-5 (4f, 1 65), D Delaney 0-2, J Phelan, C Collier, M Collier 0-1 each
CAMROSS: T Doran; M Burke, M Moloney, M Phelan; A Collier, G Burke, D Keenan; Z Keenan, A Moore; D Palmer, M Burke, D Gilmartin; D Delaney, C Collier, J Phelan.
Subs: M Collier for Gilmartin (13), A Mortimer for T Burke (46, inj), K Lalor for J Phelan (58)
RATHDOWNEY-ERRILL: A Kavanagh; A Delaney, B Campion, J Corrigan; L O’Connell, P Mahon, J Fitzpatrick; S Dollard, P Purcell; T Dowling, D King, E Meagher; M Kavanagh, R King, J Purcell.
Subs: D Bowe for D King (40), J Ryan for Meagher (45), P Meehan for Dowling (54), Lar Mahon for Campion (58)
Referee: J Lalor (Shanahoe).