Despite driving rain and swamp-like conditions Thorne put in a skilful performance and also secured a bonus point for scoring seven tries.
Thorne’s forwards dominated the first half at the set-piece. Prop Martin Moffat went over for the first try and full back Stephen Shaw ghosted through to score the second.
Further tries from Stuart Hughes and Adam Smith secured the bonus point before half time as Thorne led 22-0 at the break.
Luke Perry made good driving inroads for Thorne in the second half but Rotherham were resurgent and scored two tries, one converted to make the score 22-12.
Thorne rallied with two tries from Rob Brown and one from Robert Moffat, the latter converted by Brown.