Dagnall converted from the spot and Chris O'Grady grabbed the winner to ensure Rochdale moved to within a point of League Two leaders Bournemouth.
"It was a good game between two good teams," Hill said. "The equaliser came quickly and the game changed on that penalty decision.
"I'm not sure whether it was a penalty or not - sometimes you get them, sometimes you don't. Notts County will feel robbed and hard done to.
"I was really proud of the performance. We defended solidly and threatened on the counter attack, which may sound a bit alien for us at home."