Midfield duo Jason Knight and Josh Cullen have linked up with the squad as well as defenders Darragh Lenihan and Ciaran Clark ahead of the UEFA Nations League match against Wales.
Shamrock Rovers midfielder Jack Byrne and Swansea City's Ryan Manning have also linked up with the squad ahead of training at the Cardiff City Stadium later this evening.
Seamus Coleman, John Egan and Harry Arter have returned to their clubs.
Republic of Ireland squad
Goalkeepers: Darren Randolph (West Ham United), Caoimhín Kelleher (Liverpool), Mark Travers (AFC Bournemouth)
Defenders: Matt Doherty (Tottenham Hotspur), Kevin Long (Burnley), Shane Duffy (Celtic), Dara O'Shea (West Bromwich Albion), Cyrus Christie (Nottingham Forest), Ciaran Clark (Newcastle United), Darragh Lenihan (Blackburn Rovers), Ryan Manning (Swansea City).
Midfielders: Conor Hourihane (Aston Villa), Jeff Hendrick (Newcastle United), Jayson Molumby (Brighton and Hove Albion), Robbie Brady (Burnley), Jack Byrne (Shamrock Rovers), Jason Knight (Derby County), Josh Cullen (Anderlecht).
Attackers: James McClean (Stoke City), Adam Idah (Norwich City), James Collins (Luton Town), Ronan Curtis (Portsmouth), Callum O'Dowda (Bristol City), Daryl Horgan (Wycombe Wanderers), Sean Maguire (Preston North End).