Wales drop North as Gatland rings changes for France in Six Nations
Roberts and Watkin were named in coach Warren Gatland's team announced Wednesday instead of the established midfield pair of North and Nick Tompkins.
North and Tompkins, who have 155 caps between them, have been omitted entirely from the matchday 23 with the Welsh Rugby Union making it clear that neither is injured.
The Principality Stadium match will be Roberts's first Six Nations start after the Llanelli centre made his Test debut against Rugby World Cup warm-up opponents England last year, with Watkin recalled after featuring in the tournament opener with Scotland.
"I think it is an opportunity to have a look at Joe," Wales assistant coach Mike Forshaw told reporters on Wednesday after Gatland announced his side. "I think Joe was unlucky not to go to the World Cup.
"We just felt if we were going to have a look, this was the game to do it. He (Roberts) is a really promising young 13 going forward, and Owen Watkin has a lot of experience."
Forshaw added: "They (North and Tompkins) are not injured. Nick and George have been spoken to. They firmly believe in what we are doing.
"I don't think they have been dropped. They have had two games together and they have done extremely well. But we have got to see Joe playing, and we are going to see him."
Meanwhile, Wales captain Dafydd Jenkins has been switched to blindside flanker from lock, with Will Rowlands now partnering Adam Beard in the second row.
It will be the first time Jenkins has worn the No. 6 shirt for either club or country.
"I don't think it is a risk with Daf at six," Forshaw said.
"He is around two very smart back-rowers (Aaron Wainwright and Tommy Reffell).
"Will Rowlands played 70 minutes on the weekend in Paris (for Racing 92). I saw glimpses of him getting back to his best. I think it is a good fit for us this week."
Wales have lost their last four Championship matches against France but Les Bleus have struggled this season following the disappointment of failing to win the World Cup on home soil, with Fabien Galthie's side beaten by Ireland before edging past Scotland and then being held to a draw by Italy.
Nevertheless, Gatland said: "It'll be a tough, physical challenge from France on Sunday, particularly up front.
"We know they will start hard and it's about us staying in the fight, having good line speed defensively and keeping our discipline. We're looking for an 80-minute performance."
Galthie is due to name his side on Friday.
Wales (15-1)
Cameron Winnett, Josh Adams, Joe Roberts, Owen Watkin, Rio Dyer; Sam Costelow, Tomos Williams; Aaron Wainwright, Tommy Reffell, Dafydd Jenkins (capt); Adam Beard, Will Rowlands; Keiron Assiratti, Ryan Elias, Gareth Thomas,
Replacements: Elliot Dee, Corey Domachowski, Dillon Lewis, Alex Mann, Mackenzie Martin, Gareth Davies, Ioan Lloyd, Mason Grady
Coach: Warren Gatland (NZL)
