Billy Root, who had been dropped on naught, made the highest score by a Glamorgan batsman against Northants to put his side in complete command at the County Ground.
Root’s career-best 229 helped his side recover from 120 for five to close the second day 452 for nine, leading by 243.
And Rowe said: “It was a long day in the dirt.
"We’re really disappointed because we think we bowled quite well for a lot of the day but dropped our chances, including Billy on naught, and he made us pay.
“We created enough chances to be batting at tea time ourselves but the ball went soft, the wicket flatted out, they were in and they went on and they punished us hard.
"It’s a harsh lesson, but a lesson we continue to be given.
“When the ball is new and it nips around, our bowlers are excellent but when it gets flatter, we’ve struggled to keep control and have conceded a run-rate which can keep us in the game.
"That’s what we’ve got to improve.”
While Northants, who were all out for just 209 on the first day, having lost the toss, have yet to win in the Championship this season, Glamorgan have enjoyed an early-season revival.
And Root said: "When I first went it it was tricky and I was focused on getting through little periods of the game and then could score more freely later in the day.
“It was nice to have a few partnerships - Dan (Douthwaite) and Tom (Cullen) played really well so it was good to have those guys hanging around.
“My first 30 runs were through third man and I was dropped on naught so I’m glad I made the most of my fortune.
“We’re now in a great position and hopefully we can now back up our position with the ball.”