In addition the visitors cause was not helped by he dismissal of Rhys Thomlinson early in the second half for foul play and although Rossendale continued to battle, down to 14 proved to much of a handicap as Lymm ran in a total of five tries.
Lymm opened with a penalty from Richard McEvoy soon followed by a try by Adam Bray, McEvoy on hand with the extras.
Steve Nutt slotted a penalty to get the east Lancashire on the scoresheet before McEvoy crossed the line himself also kicking the conversion.
Nutt knocked over a second penalty for 17-6 at the break.
In the second half with Rossendale forces depleted Lymm added two further tries through Ross White and James Kimber, converted by McEvoy but despite being low on numbers good pressure by the pack from a series of rolling mauls created the opportunity for James Bramhall to go over for the visitors, the scrum half spotting the gap after the Lymm defence had been sucked in.
Lymm came back with a second try from Bray, McEvoy again on target but Rossendale hit back strongly at the end with a break by Tom Earnshaw and through good support play from the pack Jordan Lord was on hand to take the scoring pass, Nutt adding the extras.
Geoff Lightfoot