The 21-year-old featured regularly once again at left-back last season for the Brittany-based side who finished fourth in Ligue 1.
Truffert registered seven assists for the club last season, and was rewarded with his first French cap by Didier Deschamps against Denmark last September.
Despite his young age, Truffert has already made 113 senior appearances at the club where he has spent all of his professional career so far.
Foot Mercato claims that Truffert will continue his journey with the club too, as he is expected to sign a two-year extension to his current deal.
Forest had allegedly made Truffert their top priority to replace Renan Lodi, who opted to join Marseille instead of making his loan move at the City Ground permanent.
However, with Truffert now expected to remain at Rennes, the club will have to look elsewhere for an alternative.
Another Ligue 1 left-back has been rumoured to be on Forest's radar, as Monaco's Ismail Jakobs has been linked.
Jakobs could be a more attainable target given that he is currently only second choice at the Stade Louis II behind Brazilian Caio Henrique.
Full-back Ola Aina has also been brought in this summer by Steve Cooper, but while showing his ability to be versatile at Torino, the Nigerian is more comfortable on the right.
While the club looks to add to their squad, they also have a mounting problem regarding contract expiries.
Forest have 15 players entering the final year of their contracts at the City Ground, one of whom is captain Joe Worrall.
However, Football Insider claims that the club are keen to sit down at the negotiating table and agree a new deal with the central defender.
The 26-year-old came through the youth ranks at the club and has since made over 200 appearances in a Forest shirt, so the club would prefer not to lose their skipper on a free next summer.
The report states that there is a willingness from all parties to get a deal done, with Forest keen to do so before the season starts.
Worrall was in and out of Cooper's side often last season, but he was a regular during the run-in, helping the Midlands side to survive relegation.
An injury to Moussa Niakhate also means that Worrall is expected to start the season in the side, so having him tied down to a new deal would help avoid any potential distractions from preparing for the new season.