Second half goals from substitute Kayode Odejayi and midfielder Lee Frecklington were enough to earn the points for Steve Evans' men, who defeated the form side in the division since John Ward returned to the Memorial Stadium.
In a first half that saw a couple of good openings, it was Frecklington who missed the best chance for either side, lobbing over Steve Mildenhall in the home goal, but also the crossbar, after Alex Revell's knock down.
Revell also went close himself but was just unable to reach Kieran Agard's low cross with the goal gaping.
John-Joe O'Toole had Rovers best effort of the half as he drilled into the side netting from 20 yards.
But the Millers started brighter after the interval and stormed into a two goal lead just after the hour.
Firstly Revell raced clear on the right only to see Mildenhall parry his right foot shot back into the path of Odejayi, who composed himself to take a touch then slot the ball home.
Then two minutes later, half time sub Odejayi turned provider as he laid the ball off following Kari Arnason's long throw for the on rushing Frecklington to smash the ball into the top corner.
Joe Anyinsah netted the goal of the game with ten minutes left as his fierce drive flew past Andy Warrington from the corner of the 18 yard box, but it was in vain as Rotherham made it three wins in a week to continue their good form.