It needed the introduction of substitute Gary Teale to break the deadlock in the 69th minute, before Jason Roberts hit the second goal into
stoppage time.
Lee McCulloch also hit the woodwork while Millers keeper Mike Pollitt pulled off two fine saves, but Jewell wasn't overly impressed.
He said: "We did okay but we weren't really at the races.
"Good football didn't win us the game and I didn't think our organisation was the best.
"We normally have two good banks of four which is hard to break down, and while Rotherham didn't have too many chances, I thought there were too many gaps across the pitch.
"It means we have a lot of work to do in training this week so we can hopefully improve for the Watford game on Saturday.
"Although I wasn't best pleased with them, it was still a valuable three points for us.
"The important thing at this stage of the season is results rather than performances, but as a manager, you hope for both.
"I suppose I shouldn't complain too much because this was our third win and clean sheet in a row.
"We were up against a very hard working and honest Rotherham team who didn't look like a side down at the bottom."
A boost for Jewell was seeing Teale on the scoresheet for the first time since February last year, his goal coming just six minutes after replacing David Graham.
He has now urged the winger to take confidence from the strike and push on to try to earn a new contract.
"Tealey knows he hasn't done as well as he did last year, and maybe this will give him a kick on," said Jewell.
"He is a good player and a good pro, and hopefully the goal will have done something for his confidence.
"He has got 17 games left of the final year of his contract and he knows what he has to do.
"I put him on because I thought he might stretch their defence a bit more, up until then we'd been playing in front of them too much.
"We had started with David Graham out on the right but we know he is more of a striker.
"I also changed things at half-time, replacing Gareth Whalley in the midfield with Mike Flynn.
"It wasn't a game where Gareth was making much of an impact and I just put Flynny in there for a bit more energy and to be more dynamic.
"He managed to miss one from a yard out which he did well to do, but I thought he had a positive effect on the game."
Jewell resisted the temptation to freshen up the squad with the addition of new signing Andreas Johansson.
The Swedish midfielder did travel to Millmoor, though, training on the pitch beforehand to improve his fitness.
There was no news from Jewell concerning any further dealings on the transfer front, although the club continues to get linked with players on
soccer's grapevine.
Middlesbrough's 19-year-old striker Danny Graham is a rumoured target having forced his way to the fringes of Steve McClaren's squad this season.