The 31-year-old, who can play either lock or in the back row, has been an ever-present in the league this season.
Head coach Richard Hill said: "It is fantastic news that Roy has signed a new two-year contract with us. He is an incredibly hard-working member of the pack and a great team player who is constantly trying to raise his game.
"This signing shows Bristol's determination to remain a successful and improving Guinness Premiership outfit and Roy will play a significant part in our plans for the future."
The 6ft 4ins, 17st 8lbs Winters joined Bristol for Harlequins in May 2005.