Ian Henderson did not enjoy the best of times at Sixfields earlier in his career but he returned to play a big part in the win for Hill's men on Tuesday night.
Having notched his 10th goal of the season early on, Henderson set up Joe Bunney for the crucial third goal following Matthew Lund's dismissal for over-celebrating just after he had doubled Dale's advantage in the second half.
And Rochdale manager Hill was full of praise for the new leaders.
He said: "We were very good. Northampton have been good lately and (Cobblers manager) Chris Wilder has done an excellent job here because he's got them in a position where they have got a very good chance of surviving.
"I think they'd won three and drawn three before this game and maybe we took them by surprise a little bit.
"The pitch was superb and that helped us, it was the perfect night for us really. We dominated chances on the counter-attack and that is very important but we did that because we've got good players at the club.
"I'm not on my third squad here, I'm on my first squad and I haven't gone to the chairman or the board of directors and asked them for loads of extra money.
"I trust the players that I've got at the football club and it's just another game. We've got nine games left and I'm looking forward to them."
Wilder saw his side slip to their first defeat in seven outings and he knows he must pick them up for Saturday's trip to Morecambe, who were also on the wrong end of a heavy defeat on Tuesday night as they lost 5-1 at Accrington.
It was the second game running that Wilder's side had failed to overcome 10 men and he said: "I've got no complaints about the result. I will always praise the opposition and all credit to Rochdale who were excellent.
"It was really poor to concede such an early goal, that gave them a foothold in the game. We began to get on the front foot but we had to be careful not to get caught on the break.
"We weren't good enough, we're big enough to admit that. It's three points lost and thankfully no more because of a poor performance. Our service to the front two wasn't good enough but Rochdale set up well and didn't let us get going in the final third.
"We've made some big strides since we've been here but we've taken a backward step. Hopefully, it's a one-off because we can't let that happen over the next few games.
"We're not happy as a staff with that performance and the players should feel the same. But it's no use me slaughtering the players, now it's up to them to go again at Morecambe on Saturday.
"I always knew it was going to be a tough challenge when I came here but I still believe we will get out of trouble."
- Sports & Recreation
- Chris Wilder