And with rivals Sunderland losing to Coventry in a nine-goal thriller, it means the sides – along with Barnsley – bunched even tighter in the table.
Oli Hawkins headed the opener at a packed Fratton Park, with Brett Pitman adding a penalty just before the break.
Aaron Wilbraham raised hopes of a Dale comeback early in the second half, but Evans came off the bench to calm fears before Jamal Lowe wrapped up a sixth successive win.
Kenny Jackett made one change from the side that won at Wycombe seven days earlier.
A fully-fit Ronan Curtis replaced Evans wide on the left, while Louis Dennis’ goal for the reserves earlier in the week saw him named among the substitutes.
The hosts started brightly in the spring sunshine and looked to get at their opponents right from the off.
Lowe was unable to force the ball home from a tight angle, while a cross from Curtis was just too high for Hawkins.
But as the sun went behind the clouds, Pompey also faded slightly and when Craig MacGillivray failed to hold a Callum Camps corner, Tom Naylor was forced to hack clear.
Matt Done then sent a dangerous delivery into the mixer, although a well-placed Ian Henderson headed it wide.
The Blues soon picked things up, however, and Hawkins should have done better than divert Lee Brown’s free-kick into the arms of a grateful Josh Lillis.
But HAWKINS did find the target midway through the first half, arriving at the near post to firmly head home Lowe’s cross.
Lowe might have doubled the advantage moments later, only for Lillis to come racing from his line to make the save.
Rochdale then had an opportunity of his own, when Wilbraham beat MacGillivray to a Christian Burgess pass, but could not beat the keeper.
It was the Blues looking the more likely to add to the scoring, though, and Hawkins nodded narrowly over after meeting Brown’s delivery.
He then saw another header saved by Lillis, while Ben Close had an attempt blocked as the hosts continued to apply pressure.
And it paid off just before the break when Nathan Thompson collected Lowe’s threaded pass and was crudely brought down in the box by Ethan Ebanks-Landell.
Referee Lee Swabey had no choice but to point to the spot and PITMAN calmly sent Lillis the wrong way to give Pompey a commanding interval lead.
The visitors looked brighter immediately following the restart, although Jim McNulty’s header was never going to prove much of a test for MacGillivray.
But Pompey were still looking dangerous going forward themselves and were causing plenty of problems for Dale to deal with.
One attack actually led to a goal for the opposition, however, with a quick break up the pitch ending with Done squaring for Wilbraham to slot into the net.
Pompey immediately looked to hit back and a long-range curling effort from Pitman was pushed behind by Lilllis.
The resulting corner almost provided a goal, with Burgess nodding it into the mixer and – in a sea of bodies – the ball eventually being hacked clear.
Jackett soon made a substitution, with Curtis – who had been quiet on the left – making way for Evans.
And it was EVANS who restored the two-goal lead just past the hour mark, nodding home from a few yards out after Lowe had lifted the ball into the centre.
Pompey were searching for a more convincing scoreline and a Brown cross was just out of reach for Lowe, while a rushed Hawkins effort was comfortable for Lillis.
They were starting to sit a bit too deep in the closing stages, though, and Jackett tried to add fresh impetus by replacing Hawkins with Omar Bogle.
But it was a Rochdale sub who had a chance to score moments later, although Bradden Inman slipped as he got his shot away and MacGillivray saved low to his left.
And Pompey immediately wrapped things up at the other end, as LOWE collected Matt Clarke’s long pass, held off one challenge and got past Lillis before firing the ball into the net.
Jackett’s final change saw Bryn Morris come on for Pitman, although it was fellow substitute Bogle whose effort had to be clawed away by Lillis.
Brown should have given the scoreline an added gloss late on, but glanced Lowe’s delivery wide with the goal gaping.
It mattered not, however, as Pompey had comfortably done enough to extend their winning run and move to within two points of second place.
Pompey (4-2-3-1): MacGillivray; Thompson, Burgess, Clarke, Brown; Naylor, Close; Lowe, Pitman (c) (Morris 82), Curtis (Evans 57); Hawkins (Bogle 76)
Goals: Hawkins 21, Pitman 45+1 (pen), Evans 62, Lowe 79
Subs not used: Bass, Walkes, Haunstrup, Dennis
Rochdale (4-2-3-1): Lillis; McLaughlin, Ebanks-Landell, McNulty, Bunney (MJ Williams 67); Camps, Hamilton; Done (Inman 75), Henderson (c), Rathbone (Clough 80); Wilbraham
Goals: Wilbraham 54
Booked: Wilbraham, Ebanks-Landell, Bunney
Subs not used: Wade, Keohane, Dooley, Andrew
Referee: Lee Swabey
Attendance: 18,197 (188 away fans)