Fletcher enjoyed a brilliant start to the season with the red ball, his 36 County Championship wickets coming at an average of 22.44, and will take his association with the Club past the ten-year mark with his newest deal.
However, his season was cut short after he was hit on the head during his follow through during a NatWest T20 Blast encounter against the Birmingham Bears.
Root meanwhile, made his List A and T20 debuts for the Club this summer, averaging 64.75 in the Royal London One-Day Cup, including an unbeaten century against Warwickshire.
The two-year deal is the 25-year-old’s first professional contract with the Club, as the all-rounder and Fletcher join Jake Libby in recently signing new deals.
“It’s a well deserved contract for Luke because of what he has done in the last 12 months,” said Head Coach Peter Moores.
“He’s gone away and looked quite hard at what he can do to get himself into the team and then play the kind of cricket where he can contribute to making us competitive.
“He got himself in good shape and, straight away on our tour in Barbados, he impressed everyone with how he was going about his work.
“We have seen the results of that in the way he bowled in the first part of the County Championship season and in helping us to win the Royal London Cup.”
The Bulwell Bomber has taken over 350 wickets across all three formats since making his debut for Nottinghamshire at the start of the 2008 season.
“Luke has proved a lot to himself by showing that he can go to another level as a player and, as a Notts lad and a heartbeat of the team, we’re delighted to get him tied up for another two years,” added Moores.
“It’s been disappointing for him to get injured in the T20 competition and miss the end of this season, but I’m sure he will come back strongly in 2018 and hungry to do well.”
Meanwhile, Moores has now challenged Root to push on in all three formats in the coming years.
“Billy worked very hard in the off season and used his bowling to help get him a chance in the side from where he could show what he could do with the bat as well,” said Moores.
“He’s been an effective player for us, particularly in one-day cricket, and we’re looking for him to now push on in both white and red ball cricket after working very hard for this opportunity.
“As a younger player it is sometimes difficult to understand your own game and get the basics right that will help you become a more consistent cricketer, but we feel Billy is starting to do that.
“It’s particularly difficult now with the switches between 50-over, 20-over and Championship cricket, it’s quite a lot to get your head around, but he is starting to put it together.”