Jolly left the Swans for the Magpies at the end of 2009 after five successful years in Sydney, and has shown strong recent form after a slow start to his career in black and white. But Roos was confident that his new-look combination of Mumford and the rapidly-improving Pyke would give the Swans a great start in the midfield as they seek to end an eight-game losing streak against Collingwood.
"Pykey will know [Jolly] a bit better than what Mummy will, but our ruckmen have been really solid, particularly over the past two weeks since Mummy's been back," Roos said on Monday.
"Without [Mark] Seaby, a lot of credit has gone to Shane, but I think Pykey's done a really good job as well.
"It's a credit to him how far he's come in such a short space of time … he's been a real positive for us in the last couple of weeks.''
Roos even said Pyke's improvement could create a welcome headache when Seaby makes his expected return from a broken ankle later in the season.
"If Seabs comes back and gets fit, obviously his form earlier in the season was really good, so it's actually a good position to be in, to have three ruckmen in pretty good form," he said.
"We'll deal with that if and when it happens."
Rhyce Shaw (hip) is expected to return against his old side after he was a late withdrawal against Port Adelaide, and Roos confirmed that key forward Daniel Bradshaw (knee) was on track to resume.
"He ran yesterday for about the third or fourth time. We're looking to train him tomorrow for about 20 minutes and then train him again on Thursday," Roos said of the club's leading goalkicker in 2010.
"At this stage, he's done everything to get to this point and providing he doesn't pull up sore after training tomorrow or training Thursday, we certainly expect him to play."
The Magpies have stuttered in recent weeks after a strong start to the season, taking two wins and a draw from their past four games. But Roos said form often went out the window when Collingwood travelled north to ANZ Stadium.
"They seem to be one team that form prior to our games doesn't really come into it," he said.
"They play some of the best football of the year against us and often the week after, whether they get themselves up for us as a team or not, I've seen them play poorly."
The Swans suffered a 23-point loss in the corresponding clash last year after Alan Didak and Leon Davis fired the Pies to a four-goal final term, and Roos said a four-quarter effort would be critical on Saturday night.
"A couple of their good players just seem to bob up at the right time. Didak, Leon Davis … Daisy Thomas a couple of years ago," he said.
"Certainly they've got a lot of quality players, and they're always hard to contain for a full game."
