The striker had been ruled out for at least the next fortnight, but managed a full training session with the squad yesterday.
If there's no adverse reaction from that workout, he will go straight into the side at Fratton Park (kick-off 5.15pm).
With Lee McCulloch also available again after his ban, manager Paul Jewell suddenly has selection options up front after being down to one striker against Fulham a week ago.
Roberts tore a muscle in the upper part of his thigh at Aston Villa 13 days ago and the earliest he was expected back was for Arsenal's visit to the JJB Stadium on November 19.
His recovery has even caught Jewell by surprise, but it's a welcome one as Latics look to make it six league wins on the bounce.
Jewell said: "Jason has made rapid progress from his injury and while we won't take any risks, we'll see how he is for tomorrow. He trained yesterday morning and if he comes through with no reaction, he'll be available for selection.
"People have different powers of recovery, no one is the same, and that's why it is hard putting a timescale on how long players will be out for.
"I thought Jason had no chance for tomorrow but now he has a fair chance of playing and that's a boost.
"Last week we only had one striker, this week we could have three if we want, and that's the competition we need."
If Roberts comes through, he'll be facing one of his former clubs, having had a four-month loan spell with Pompey immediately prior to moving to the JJB.
Latics' other main injury worry, David Connolly, definitely won't be fit to travel to the south coast.
The striker is making decent progress trying to shake off a hamstring strain but Arsenal looks a more realistic target.
Jewell said: "He's had a scan which shows the problem is not in his back, it's just a niggle, and after tomorrow he has two weeks to get it exactly right."
Providing Roberts is fit, he would partner Henri Camara up front with McCulloch likely to be restored to the left-side of midfield.
McCulloch had been on stand-by to play as a centre-forward, but his physical
presence in the wide role would prove welcome for second-placed Latics.
Jewell will demand one more big effort from his players tomorrow before the two-week international break.
He said: "We have one objective which is to stay in this league, and the quicker we have the points on the board, the better," said Jewell.
"We are enjoying it but we're not basking in it.
"Everyone enjoys coming in for training and working hard, and competition for places is intense.
"Portsmouth is another tough game for us, it's a tough place to go, but it's one we're looking forward to."
The game is being shown live on Sky Sports 2.
If there's no adverse reaction from that workout, he will go straight into the side at Fratton Park (kick-off 5.15pm).
With Lee McCulloch also available again after his ban, manager Paul Jewell suddenly has selection options up front after being down to one striker against Fulham a week ago.
Roberts tore a muscle in the upper part of his thigh at Aston Villa 13 days ago and the earliest he was expected back was for Arsenal's visit to the JJB Stadium on November 19.
His recovery has even caught Jewell by surprise, but it's a welcome one as Latics look to make it six league wins on the bounce.
Jewell said: "Jason has made rapid progress from his injury and while we won't take any risks, we'll see how he is for tomorrow. He trained yesterday morning and if he comes through with no reaction, he'll be available for selection.
"People have different powers of recovery, no one is the same, and that's why it is hard putting a timescale on how long players will be out for.
"I thought Jason had no chance for tomorrow but now he has a fair chance of playing and that's a boost.
"Last week we only had one striker, this week we could have three if we want, and that's the competition we need."
If Roberts comes through, he'll be facing one of his former clubs, having had a four-month loan spell with Pompey immediately prior to moving to the JJB.
Latics' other main injury worry, David Connolly, definitely won't be fit to travel to the south coast.
The striker is making decent progress trying to shake off a hamstring strain but Arsenal looks a more realistic target.
Jewell said: "He's had a scan which shows the problem is not in his back, it's just a niggle, and after tomorrow he has two weeks to get it exactly right."
Providing Roberts is fit, he would partner Henri Camara up front with McCulloch likely to be restored to the left-side of midfield.
McCulloch had been on stand-by to play as a centre-forward, but his physical
presence in the wide role would prove welcome for second-placed Latics.
Jewell will demand one more big effort from his players tomorrow before the two-week international break.
He said: "We have one objective which is to stay in this league, and the quicker we have the points on the board, the better," said Jewell.
"We are enjoying it but we're not basking in it.
"Everyone enjoys coming in for training and working hard, and competition for places is intense.
"Portsmouth is another tough game for us, it's a tough place to go, but it's one we're looking forward to."
The game is being shown live on Sky Sports 2.