Rees-Zammit, who last played for Wales at the 2023 World Cup, joined the Kansas City Chiefs and then the Jacksonville Jaguars but did not feature in a competitive NFL game before signing with Bristol in August.
The squad, announced by new head coach Steve Tandy, includes Jac Morgan returning as captain after missing the summer tour, and features five uncapped players.
Rhys Carre is also back in the squad following confirmation of his eligibility, despite playing for a club outside Wales and being five caps short of the usual requirement.
Will Rowlands has announced his retirement from international rugby, while several other players, including Josh Macleod and Teddy Williams, are ruled out due to injury.