North Wales Crusaders missed the chance to close the gap on Oldham at the top of League One after losing 23-6 at home to the Roughyeds on Sunday.
Rhys Evans' try ensured the Welsh side only trailed 12-6 at half-time.
But some fine Oldham defence, plus a try from George Tyson and Steven Roper's kicking ended Crusaders' hopes.
League One bottom side South Wales Scorpions were given a 64-0 home thumping by York City Knights at Mountain Ash on Saturday.
Kristian Brining's hat-trick spear-headed an 11-try rout by York, with James Haynes kicking 10 goals.
The result ensured it is now 56 weeks since a southern side beat one from the north in League One.