Hoskins, signed from Watford in the summer, struck a rising drive into the top right corner in the final seconds of time added on. There was barely enough time for Huddersfield, who had Jamie McCombe sent off for picking up two yellow cards, to kick-off again.
The Terriers, who dominated possession and created a stack of chances, were their own worst enemies in front of goal and have now failed to score in three consecutive games.
Scott Arfield blazed over from inside the six-yard box in the 11th minute when the Rovers' defence failed to clear Anthony Pilkington's corner.
Carey then wasted an even easier chance in the 55th minute when he volleyed over unmarked from close range after Pilkington had swung over a teasing cross.
Huddersfield's frustration was complete when McCombe, booked in the first half for a foul on John Akinde, hauled down Hoskins and was given his marching orders by referee Karl Evans.