Leading scorer Ellington now has 18 for the season while Roberts' brace took his total to eight in just 12 starts.
Eight of Ellington's goals have come since being teamed up with Roberts in January, and they are now regarded as one of the most feared pair of strikers in the First Division.
But Jewell is still pushing for more from them as Latics seek the six points or so points necessary for a top six finish.
He said: "I ask my strikers to work just as hard off the ball as they do when they've got it. It's important they stay switched on when the opposition are in possession rather than having a rest.
"That is becoming second nature to the Duke now because he's been here longer than Jason has.
"If you look at some of the great strikers, Ian Rush for example, he was always moving, always working.
"With the power and pace our two lads have got, they can sometimes be unplayable.
"But I'm always looking for improvement, even though Jason has eight in 12 games since he came here. As well as those two, we have got some other good strikers here, with Lee McCulloch and Neil Roberts in the squad.
"It's nice to look round at the bench and see those two as they work their socks off."
Jewell admits his strikers can't be scoring all the time, and wants to see a bigger goals contribution from other areas of the team.
In the last 13 games, only Gary Teale and Alan Mahon have come from deeper positions to score in open play.
Midfielder Jimmy Bullard's last goal was before Christmas, while Jason Jarrett hasn't been on target since August.
Goals have been in short supply from the defence too, skipper Jason de Vos the last defender to score against Crewe in December.
Jewell said: "I like my strikers scoring lots of goals and it's a good job they are doing that.
"All jokes aside, it would be nice to get a couple of goals from other areas of the team, certainly from central midfielder and at set-plays.
"Sometimes you need to take the pressure off the front two and spread the goals around a bit."
* Latics Reserves beat Macclesfield 3-0 at Robin Park Arena yesterday.
* Tickets for the away game at Nottingham Forest on May 1 are now on sale to season ticket holders. They will go on general release a week on Saturday.
They cost £22 adults, £15 Over-60s, £10 Under-16s and students
Source: Wigan Evening Post.
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