Craig Morgan and Ben Pringle have rejected new contracts at Rotherham and will leave the club on free transfers.
Saido Berahino can leave West Brom "if the deal is right", says manager Tony Pulis.
The 25-year-old striker has attracted interest from several of Europe's top clubs with his performances for current club Celta Vigo - and Michael Laudrup was rumoured to be lining up a move.
But his agent, Felix Gende, said: "It's clear that there are a lot of clubs following Iago because of the season he is having, but right now it is impossible that he leaves for another club in January.
"He is focused on helping his team retain their Primera Division status. Come June, when there are a lot more transfers, God will say what happens with his future."
Aspas' 23 goals last season inspired Celta to promotion to the Primera Liga, and he has netted six times this season in Spain's top flight.