Second-half goals from Kal Naismith and Conor Chaplin earned Pompey a hard-fought 2-0 victory at Hartlepool.
Results elsewhere now mean the Blues are guaranteed to face Plymouth in the League Two play-offs.
The opening goal for Paul Cook’s men arrived on 57 minutes as Naismith back-flicked the ball into the net after a low cross from Gareth Evans.
Substitute Chaplin then slid the ball into the net in style after Enda Stevens cut the ball back from the left flank.
It was enough to win a contest that didn’t spark in the first half but came to life after the break.
Roberts threatened early on two minutes for Pompey and after twisting his way into a shooting position his effort hit Naismith to deflect wide of the near post.
Nathan Thomas saw his tame shot easily saved by Brian Murphy as Hartlepool had the first effort on target on 39 minutes.
The visitors responded and Roberts set Evans away through the Hartlepool defence but former Pompey loan keeper Trevor Carson saved his shot.
The ball came back to Evans but Carson reacted quickly to gather the second effort.
Pompey took the lead on 57 minutes with a moment of brilliance from Naismith.
Roberts sent Evans away on the right and his low cross was superb flicked into the net by the former Hartlepool man.
Pompey keeper Murphy saved from Billy Paynter, before Roberts saw his thumping effort deflected the wrong side of the post.
Smith then burst clear of the Pools defence but his shot was well saved by Carson.
Rhys Oates replaced Paynter up front for Hartlepool and twice missed good chances to equalise.
Murphy got out quickly to make a smart save when the striker threatened with his first touch.
Then a cross from Thomas was headed well over the top by Oates.
Pompey wrapped up the win on 85 minutes when Stevens burst down the left and perfectly picked out Chaplin who slid the ball calmly into the far corner of the net.
It was another moment of quality from the young forward to complete a good win for Cook’s side.
They are now set for a play-off battle with Plymouth.