After snapping up Collins following his release by the Reds, Rotherham boss Steve Evans has landed his 'top target' by signing 30-year-old Halford.
Evans received a 'huge endorsement' of the player from his fellow Scot, former City Ground boss Billy Davies and Halford and Collins, together with Derbyshire who moved to Rotherham last summer, could all be in action against their old club very soon.
The Millers visit for Forest's first home league game of the Championship season on Saturday 15 August.