Roberto has endured a disastrous six months at West Ham that saw him make a string of errors when he came into the team for the injured Lukasz Fabianski.
The 33-year-old is set to return to Spain to join Alaves on loan until the end of the season. The deal is expected to be finalised on Monday.
Roberto joined West Ham on a free transfer last summer to provide experienced cover for Fabianski but it soon became clear he was not good enough.
He punched a corner into his own goal in a 3-0 defeat at Burnley in November and conceded 22 goals in 10 matches before he was dropped.
West Ham have signed Darren Randolph for £4million after losing faith in Roberto and the Spaniard has no future at West Ham.
Roberto, who was recommended by former director of football Mario Husillos, still has 18 months left on his contract but the Hammers will look to sell him on a permanent basis in the summer.
In Pictures | West Ham vs Everton | 18/01/2020
Randolph made a solid debut in Saturday’s 1-1 draw with Everton and the 32-year-old Ireland international has said he wants to challenge Fabianski for the No1 spot.
Fabianski is out until next month with a hip injury and Randolph said: “Lukasz is the No1 goalkeeper here but I have got a chance now to play some games and push as hard as I can.
“Hopefully it works out for the both of us that we both push each other and it is best for the club. Every team needs pressure and competition for every position. We have got a lot of games against the top teams so it gives me a chance to perform.”
MORE ABOUT