Leyton Orient were heading towards three points after being gifted an opener by Neil Cutler.
They went 2-0 up through Gary Alexander before Hoskins struck in the 69th and 81st minutes.
Rotherham, with only ten fit first-team players, started brightly with top-scorer Hoskins curling a shot just wide on seven minutes.
Justin Cochrane then had a shot saved but on 15 minutes Orient took the lead. Matt Lockwood and Wayne Corden worked the opportunity on the left and James Walker teed-up Chambers who drilled a low shot from 20 yards through a sea of legs.
Even so it appeared bread and butter for Cutler, but the ball spun out of his grasp and over the line.
Hibbert then had a goal disallowed on 29 minutes after Ritchie Partridge's curling effort had ricocheted back off the post into the feet of the offside striker.
Hoskins, a January transfer target for a host of clubs including Premiership strugglers Watford, then tried his luck from 25 yards which was beaten away by Glyn Garner.
Cutler atoned for his earlier mistake with a brilliant tip over the bar to deny Walker eight minutes before the break.
As play swung up the other end, Partridge beat two players and stung Garner's finger-tips with a close-range effort.
Orient doubled the lead seven minutes after the break. Donny Barnard lumped a high ball forward and the onside Alexander controlled it, turned and fired across Cutler.
He then equalised with a brilliant volley which looped over Garner from 16 yards nine minutes from time.