Rotherham led 11-6 at that stage but lost openside flanker Tom Calladine to the sin-bin after he was adjudged to have made a dangerous tackle.
And Moseley ruthlessly made the most of their numerical advantage to score 10 points through a Greg Charlton try and a conversion and a penalty from Charlie Foley.
The priceless win moves the Championship’s bottom-markers to within seven points of the free-falling Titans.
Rotherham had earlier got off to the perfect start when hooker Darren Harris crashed over in the corner following impressive work from the visiting pack.
Two Foley penatlies gave Moseley the slenderest of leads at the break with Rotherham unable to turn their territory into points.
Strong pack play at least created a penalty opportunity from which Ross Jones converted to restore Rotherham’s lead.
Jones’ second penalty edged Rotherham further ahead but they were unable to extend that advantage before Calladine’s sin-binning led to the dramatic turnaround which resulted in Moseley sucking the South Yorkshire club – fourth in each of the last two seasons – closer to the relegation trap door and the prospect of National One rugby.
Moseley: Evans, Cheshire, King, Molenaar, Watkins, Foley, Brown, Voisey, Caves, S. Gardiner, Charlton, Onojaife, Flagg, Brightwell, Siggery. Unused substitutes: Fidler, Tolmie, Raven, Nutley, Hudson, Stephenson, Brazier.
Rotherham Titans: Goodwin, Keating, L. Hayes, J. Davies, Scanlon, Jones, Carter, Williams, Harris, Tampin, Holmes, Oram, Argyle, Calladine, Ryan. Unused substitutes: C. Maddison, Thiede, Elliot, Cree, Birch, White, Gill.