Rhinos were close to full-strength in the opening period - when all 13 played 40 minutes - and Agar then rested everyone other than wingers Jack Broadbent and Liam Tindall for the second half.
Leeds led 18-6 at the break and their youngsters extended that to 30-10 before Rovers hit back strongly in the final quarter.
The Leeds coach reflected: “There were plenty of good bits to pick out of it on a difficult track against very physical and well-drilled opposition.”
The pre-match plan was to get some game time into the senior players and then give the younger end of the squad valuable experience and Agar felt both objectives were achieved.
“It was a tale of two halves in the way we approached the game,” he said.
“We planned on that and I thought going uphill, on a difficult surface, was always going to test us in the first half against a really well-organised, enthusiastic, physical team.
“We purposely went in not wanting to make any interchanges; we wanted to get our middles playing under a bit of fatigue and I thought we got a terrific, tough workout.”
The coach added: “The young kids in the second half started really well and they got put under the pump in the last 10-15 minutes.
“Scoreboards aren’t important, but they are competitive people so I thought being under pressure for the last 10 minutes like they were was a great learning curve for them.
“We had some really, really young, inexperienced players out there, but I thought some of our experienced players - Brad Dwyer in particular - played with terrific control and leadership.
“I thought Alex Mellor stood out too and it was a great learning experience for the kids and a really good workout for the more senior guys in the first half.”
Agar admitted the young players “got some bits wrong”, but stressed: “That’s understandable and all part of the journey and learning process for them.
“In a lot of cases, it was their first run playing senior football, but they brought a good energy, to get over the tryline first in the second half and the way they rolled them down the field was really good.
“There were some real positives and it was a good day.
“It’s not all about the scoreboard, it’s about another step in the right direction in pre-season.
“We wanted 40 minutes per player to get a really good, physical workout on the end of a tough week.”
Winger Ash Handley and second-row James Bentley were not selected and Agar said that was “just precautions”.
He stressed: “There’s no real injury concerns.
“If anything was feeling a bit tight or a bit sore, we definitely weren’t going to risk them.
“We just thought we’d rest Ash around a little bump he had.”
Leeds did pick up two knocks during the game.
“Tommy Holroyd’s rolled his ankle, we are not too concerned at this stage,” Agar confirmed.
“Cameron Smith has got a nasty bump to his eye which has blown up immediately.
“The doctor’s confident it’s not broken; fingers crossed we won’t have to get that checked out.”
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