Forshaw and Robles are among the players to leave Leeds United on the expiry of their contracts, although both have been invited to pre-season training.
Forshaw, 31, featured in only 12 Premier League games last season as Leeds were relegated, but has 123 appearances at Championship level.
Robles, 32, played six times following last summer's move from Real Betis.
Academy graduates Will Brook and Stuart McKinstry will also leave Elland Road.
Leeds are still to appoint a new manager following Sam Allardyce's exit, after failing to retain top-flight status.
Forshaw, who played 91 games for the club after his move from Middlesbrough in January 2018 was part of the last promotion-winning team under Marcelo Bielsa, although he missed much of the campaign with a hip injury.