The 20-year-old, on loan from Manchester City until the end of the season, had confirmed on Friday that he wanted to stay at Parkhead until after the William Hill Scottish Cup final against Aberdeen, foregoing the opportunity to go with England Under-20s to the World Cup in South Korea.
During a man-of-the-match performance Roberts broke the deadlock in the Ladbrokes Premiership encounter early in the second-half with a curling shot.
Steven MacLean levelled two minutes later but Hoops defender Dedryck Boyata headed the home side back in front before Roberts, who cost City a reported fee of around £11million when he moved from Fulham in 2015, grabbed a third from close range with substitute Callum McGregor adding a fourth for the treble-chasing home team.
"I think he's a player (Roberts) that of course we'd love to have here, but we have to respect he's still a Manchester City player," said boss Rodgers.
"If there's ever a possibility of doing it then of course it's something that I would look at."
With a smile, Rodgers admitted exerting his influence on Roberts' decision to stay for the cup final.
He said: "Celtic are paying his wages until the end of May. I wouldn't be doing my job if I didn't.
"But if I thought it was really against what he wanted to do then I would have sat him down and tried to convince him even more.
"It's a difficult one. He loves playing for his country. He's an English boy and played for them through the age groups, helped them get to a World Cup so of course he's got to think about it.
"I think it tells you everything about his enjoyment here and how he wants to be part of hopefully creating some history here.
"You don't get the chance to do that too many times in your career.
"He's an outstanding talent and his performance along with the team performance was really exciting."
Rodgers was also pleased with Michael Johnston and Anthony Ralston, both 18, who were included from the start, the former making his debut and the latter enjoying his first start having made two substitute appearances.
He said: "With young players it's just about timing. I've always given young players an opportunity.
"I want to ensure they go in with other good players at the right time and put them in against a team that's a test.
"I don't want them to be comfortable. I think that's important.
"Anthony was absolutely outstanding. He really impressed me as a 17-year-old and I took him away pre-season. I liked what I saw.
"Young Mikey came in to replace Scott Sinclair which is never easy, but I thought he did very well. He's a very exciting player and fast.
"He's still got a lot of growth in him but he's dynamic and when he becomes a bit better on final pass and adds goals he's going to be a big talent."
Celtic extended their unbeaten domestic run since the start of this season to 43 games - 35 in the league.
St Johnstone were the last Scottish team to inflict defeat on Celtic a year ago but manager Tommy Wright had no real complaints about the fourth loss of the season to the champions.
He said: "Celtic were excellent all day, we did the best we could against them.
"They are wiping the floor with everybody this season.
"At 4-1, with 15-20 minutes to go it could have been worse but we defended and seen the game out."