A David Noble double helped secure Bristol City's promotion from League One on the last day of the campaign.
Noble scored his first goal at home all season after seven minutes when he volleyed in at the second attempt.
Two minutes before the break Noble finished clinically again when Alex Russell cut in from the left and played the ball into his path.
Russell drilled in a third and despite a Marc Newsham header City took the points to secure second place.
The Robins lost their status in the old First Division back in 1998-1999 when they were relegated after finishing bottom of the table.
Bristol City: Basso, Orr, Carey, McCombe, McAllister (Fontaine 73), Betsy, Russell, Johnson (Skuse 32), Brian Wilson, Noble (Jevons 64), Showunmi.
Subs Not Used: Thomas, Smith.
Goals: Noble 8, 44, Russell 55.
Rotherham: Cutler, Wilson, Sharps, Fleming (Kerr 46), Brogan, Henderson (Yates 81), Cochrane, Jarvis, Woods, Facey, Newsham (Taylor 67).
Subs Not Used: Montgomery, O'Grady.
Goals: Newsham 58.
Ref: M Russell (Hertfordshire).