The Newcastle midfielder reacted angrily to being barged by the Rovers winger during the Magpies' 2-1 defeat and thumped him in the chest.
Barton went unpunished by referee Michael Jones, as he did not see the incident, but he is facing retrospective action from the Football Association.
Roberts, who scored the winner at St James' Park, feels Barton was out of order and has criticised him for picking on his passive team-mate.
"Morten's turned round to apologise if you watch the footage to say sorry about that foul," said Roberts.
"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. It's all right doing it to people who are not that way inclined."
Roberts was delighted to grab his second goal in as many games in midweek, as his future at Ewood Park remains up in the air.
He has been told he is free to move on, opening the door to a January exit, but for now he is just happy to be playing and doing what he does best.
"It's been a funny season for me," added the 32-year-old.
"I've not been involved as much as I would have liked because of different situations. There was a lot of interest in me at the start of the season but things never happened for whatever reason.
"But I'm back involved at the moment and I'm scoring a couple of goals and I'm looking forward to what may or may not happen in January."
Meanwhile, Blackburn assistant manager Neil McDonald has described Barton's actions as "foolish".
"It's obviously foolish and it's the wrong thing to do, but no doubt the powers that be will sort that out," McDonald said.
"The pictures are there, it wasn't provoked and I'm sure they will make the right decision about what to do."
When it was suggested to him that the contact Barton made with Pedersen was a "full-blooded punch", McDonald said: "Yes it was, and it was unprovoked as well, which probably makes it worse."