Goals from James Coppinger and John Marquis earned Rovers a point at Fratton Park.
Rovers boss Darren Ferguson made a number of changes, with Tom Anderson and Andy Boyle handed debuts in the centre of defence.
Alex Kiwomya was also in the matchday squad for the first time since his summer arrival from Chelsea, with Luke McCullough also alongside him on the bench for the first time in the season.
Rovers started brightly and took the lead after four minutes. Coppinger brought the ball onto his left foot inside the penalty area and fired a shot under Stephen Henderson and into the back of the net.
Darren Ferguson’s side then looked to have double their lead when Marquis nodded in Coppinger’s cross, but the assistant referee adjudged the No.9 to have strayed offside.
Portsmouth got themselves back in the game after 19 minutes, when a corner from Gareth Evans was nodded down into the path of centre-back Matt Clarke, who smashed the ball in from six-yards out.
The goal gave the home side a lift and they continued to put dangerous deliveries into the box, with Rovers debutants Boyle and Anderson standing firm at the heart of the defence.
Both sides had players booked in first-half injury time. Dion Donohue’s tackle on Matty Blair earned him a yellow card, before Christian Burgess and Marquis were also cautioned by the referee in the aftermath of the initial incident.
The home side started the second half on the front foot and had a great chance to go in front when Ben Close went through one-on-one with Ian Lawlor, only for the Irish keeper to make a good save with his legs.
Darren Ferguson then introduced Alex Kiwomya and Luke McCullough in place of Alfie Beestin and Tyler Garratt just before the hour-mark, which involved a switch in formations to three at the back for Rovers.
The changes paid off just four minutes later. Matty Blair’s work down the right earned the visitors a corner, before Marquis was left un-marked from Coppinger’s centre to nod home and put Rovers 2-1 up against his former club.
Kenny Jackett introduced Jamaal Lowe and Kal Naismith as the game entered the latter stages, with Rovers bringing on Rodney Kongolo for Coppinger.
The changes paid off for Pompey as they equalised with nine minutes remaining, a low ball into the box was prodded home at the back post by Brett Pitman to peg Rovers back once more.
The game took yet more twists and turns late on, firstly as Portsmouth keeper Henderson injured himself taking a goal-kick, and having used all three substitutes, Naismith went in goal with six minutes still to play.
Burgess was then shown a second yellow card as the game entered injury time for deliberate handball, handing Rovers the ascendancy for the final few minutes.
Their best chance fell to Ben Whiteman, but his shot from the edge of the penalty area was kept out by Naismith, meaning Rovers had to settle for a point on their travels.