Roberts was demoted after Wales started their November campaign with a thumping 32-8 loss to Australia.
British and Irish Lions centre Roberts was demoted after Wales started their November campaign with a thumping 32-8 loss to Australia at the Principality Stadium last weekend.
Howley, coaching Wales while Warren Gatland is on sabbatical with the Lions, has made six changes in total to his side to face the Pumas.
Liam Williams starts on the wing, Jonathan Davies is in at centre and Gareth Davies at scrum-half.
Sam Warburton, now fully fit, returns in the back-row with Alun Wyn Jones back in the side after the lock missed the Australia match following the death of his father.
Howley also recalled prop Tomas Francis.
Although squad captain Warburton is in the starting XV, veteran prop Gethin Jenkins continues to captain the side.
Jonathan Davies, passed fit after dropping out shortly before kick-off against the Wallabies with a tight hamstring, will partner Scarlets team-mate Scott Williams in midfield.
It was Scott Williams who found himself thrust into the starting XV last week following fellow centre Davies's late injury.
He responded by scoring Wales's lone try against the Wallabies and was one of the few shining lights as the Welsh suffered their heaviest home defeat for 10 years.
Instead it is Roberts who appears to have paid the price for a poor defensive display even though the 30-year-old has been a mainstay of the Wales team during the Gatland era.
The fit-again Liam Williams returns on the wing, with Gareth Davies in for Rhys Webb after his fellow scrum-half suffered an an ankle injury against Australia.
In the back row, Warburton is set to start at blindside flanker instead of Dan Lydiate, rather than in his regular position of openside, as part of a rejigged loose forward trio featuring Ross Moriarty and Justin Tipuric.
Meanwhile Jenkins is in line to become international rugby union's most-capped front row in making his 133rd Test appearance for Wales and the Lions, with fly-half Dan Biggar winning his 50th cap.
"Jon (Davies) has recovered from his tight hamstring and will link up with Scott (Williams) in midfield," said Howley.
"It's a blow to lose Rhys (Webb), but Gareth (Davies) is an excellent scrum-half, as he has shown on many occasions.
"We've made a number of changes in the pack. Tomas Francis starts at tighthead, and it's great to welcome Alun Wyn Jones back into the side after what has been a really tough few weeks for him and his family."
Former Wales and Lions scrum-half Howley added: "Sam (Warburton) came through the match for the Blues well last weekend and comes into the side at blindside.
"With Sam returning, we have spoken to him and we feel it's best for him to focus purely on his performance and role on Saturday, leaving the captaincy with Gethin.
"In terms of achievements, it's great to see Dan win his 50th cap, and also it's a huge honour for Gethin as he becomes the world's most-capped front-row forward."
Leigh Halfpenny; George North, Jonathan Davies, Scott Williams, Liam Williams; Dan Biggar Gareth Davies; Ross Moriarty, Justin Tipuric, Sam Warburton; Alun Wyn Jones, Luke Charteris; Tomas Francis, Ken Owens, Gethin Jenkins (capt)
Replacements: Scott Baldwin, Nicky Smith, Samson Lee, Cory Hill James King, Lloyd Williams, Gareth Anscombe, Jamie Roberts