Midfielder could face FA punishment
The controversial midfielder reacted angrily to being barged by the Blackburn winger during the Magpies' 2-1 defeat on Wednesday and punched him in the chest.
Referee Michael Jones did not see the incident but Barton is facing retrospective action from the FA.
And Roberts, who scored the winner on the night, is in no doubt that Barton should be punished.
He said: "Morten's turned round to apologise if you watch the footage to say sorry about that foul.
"We've all seen the footage, we all saw what happened, so it will be interesting to see what happens from now going on.
"Morten is a lovely lad and he's never going to say anything to be controversial or make any wild statements but you could see he was disappointed by what happened.
"From his point of view what he was saying was anyone who was watching the video will see what happens.
"He didn't want to comment too much because he wouldn't say boo to a goose and that's what makes yesterday even more disappointing."
Barton has also come under fire from Blackburn assistant manager Neil McDonald, who has described the midfielder's actions as "foolish".
McDonald said: "It's obviously foolish and it's the wrong thing to do, but no doubt the powers that be will sort that out.
"The pictures are there, it wasn't provoked and I'm sure they will make the right decision about what to do."