The Spanish coach took charge of his first game with the Londoners following the departure of Gareth Ainsworth and was heading for a win after Ilias Chair put the visitors ahead before Kelly struck.
Chair provided the first spark for the visitors when he dashed in off the left flank before curling an effort just wide of the post from the edge of the box.
With both teams struggling for form and in the relegation zone, it was no surprise to see few chances created in the opening 20 minutes.
Rotherham’s first shot on goal troubled Asmir Begovic as Christ Tiehi’s bouncing effort came through a crowd of bodies before being touched out for a corner.
They had a better opening moments later but Fred Onyedinma and Jordan Hugill got in each other’s way before the latter lashed over the top on the angle.
Hugill again got clear down the right-hand side but this time opted to try to find Sam Clucas instead of shooting and QPR survived the danger.
Chair was proving the visitors’ chief instigator and he again cut in from the left before firing off target from the edge of the box.
Onyedinma forced a parried save from Begovic and the rebound just eluded Cafu for what would have been a tap-in.
QPR went in front on 50 minutes and it was the dangerman Chair who produced the magic.
He cut inside and evaded a Rotherham challenge before curling an unstoppable effort beyond the reach of Viktor Johansson.
The away side were buoyed by the goal and almost got another through Elijah Dixon-Bonner but his effort was turned against the woodwork by Johansson.
Cohen Bramall created a good chance for the Millers as he scampered down the left and found Cafu but he could not get enough on a glancing header and it drifted wide.
Rotherham’s leveller came on 70 minutes as Bramall delivered it, with his free-kick being lashed in at the back post by Kelly.
Chair again tested Johansson with a low stinging drive but it was held onto by the Sweden international.
Rotherham were also going for the win and came close to taking the lead when Hakeem Odoffin saw his header crash back off the woodwork.
An end-to-end finale saw both sides threaten to nab the points.
Jimmy Dunne was just inches away from getting a touch on Kenneth Paal’s wicked cross for the visitors.
QPR should have won it in added on time but Johansson managed to keep out a shot from Charlie Kelman from point-blank range.