Manuel Pellegrini insisted goalkeeper Roberto has his and the other players' trust ahead of West Ham's trip to Burnley despite recent criticism.
The Hammers have conceded in every game since Lukasz Fabianski sustained a hip injury at Bournemouth in September, with the Poland international not expected to return before December at the earliest.
Roberto joined on a free transfer from Malaga this summer as back-up after Adrian departed for Liverpool, but was unable to prevent defeats by Crystal Palace, Everton and Newcastle.
When asked about Roberto's form, the Chilean said: "I think that with the experience that he has I am absolutely sure that this is not his first bad moment in his career.
"He is a player with experience. A player that played before in big teams so I don't think that he will not be able to reverse the situation.
"I continue to trust him and all the other players trust in him also."
West Ham have conceded five goals from set-pieces this season, including two during their 3-2 home defeat to Newcastle on Saturday, and Pellegrini believes the whole team is to blame rather than individual players.
"I don't talk about individual players. I talk about the team. The team is not winning and when you are not winning it is because everyone must do better, including the manager, the players and individual performances.
"As a team we need to improve, especially from set-pieces. They are not the way we want... It's something we must improve as a team rather than find one player guilty."
Burnley have been strong from set-pieces this season, but Pellegrini said West Ham have been working on defending them.
"We try to work during the week but set-pieces is just one second, one moment to win a position.
"It's not so easy. Of course, if the most amount of goals that we are conceding is from set-pieces then we need to work on that."
Burnley have lost their last three matches, but all three of their wins in the Premier League this season have come at Turf Moor.
When asked about Saturday's opponents, Pellegrini said: "You never know if it's better to play against a team when they are in a good moment or in a bad moment.
"Burnley will always be a difficult team at home. They have a very clear style of play, top players with a lot of crosses and everyone knows that.
"If we win the game it will not be because we know how they play, it will be because we play better."