Ismael made all of his permitted replacements before the second half's midway point with Carlton Morris opening the scoring after being introduced as part of a triple substitution after 55 minutes.
Ismael said: "I know that with the schedule and squad depth we have now, we have more possibility to do something with our bench after the work we put in during the transfer window.
"The first half was pretty evenly balanced in terms of the chances for both teams, but I knew the bench could win us the game and I wanted us to stay in it and then apply more and more pressure.
"Playing Chelsea and Brentford last week took a lot of energy out of us and there was a big impact from all five players who came on.
"I'm delighted about the substitute rule this season because it gives you more options to have an impact on the game and we scored at the right moment.
"At 1-0, we then had a lot of chances to finish the job but we were a bit sloppy with the final pass before Alex finally scored.
"We went on to concede a goal completely unnecessarily, but it wasn't a big deal as we won, got the points, moved up the table again and carried on our momentum. We're on 42 points now and need eight more to reach our first target this season."
Rovers boss Tony Mowbray confessed that his team need to return to winning ways swiftly if they are to keep his points benchmark within sight following a third straight loss.
He said: "I want to get between 70 and 75 points, but Blackburn Rovers haven't been tearing up this division to get in the Premier League for a lot of years and we're not alone in that respect. Inconsistency is there for a lot of teams in this division.
"There's only really Brentford who have put together a fantastic run this season. I'm sure there's an unbeaten run around the corner for us and we'll have to go on a couple if we are to make the play-offs.
"This game was what we expected from Barnsley and one that supporters will probably be happy that they missed, because it was not much of a spectacle. There was a lot of long balls and they are a very direct team who press extremely well from the front.
"We tried to nullify Barnsley's strengths but did not have the ability to deal with them and fell down on the basics in terms of the goals we conceded."