AFC Bournemouth
The World Cup hopes of Cherries duo Kieffer Moore and Chris Mepham were dealt a major blow when they were defeated by Iran on Friday.
Wales knew a win would give them a major chance of qualifying from Group B, having earned a draw with USA on Monday.
Moore had starred in that opening game and was rewarded with his first World Cup start, as Mepham continued to play at the back.
The first chance of the game fell to Moore, who met Roberts' low cross with an outstretched boot and forced a brilliant save from Iran's Hossein Hosseini.
However, their Middle Eastern opponents largely dominated proceedings and saw a first-half goal disallowed for offside.
Goalkeeper Wayne Hennessey saw red for Wales in the 86th minute and Iran secured the win with two goals in a breathless period of stoppage time.
Centre-back Rouzbeh Cheshmi scored the first with a well-hit effort from the edge of the box before Ramin Rezaeian's classy chip wrapped up the win.
Wales will now need to beat England on Tuesday to maintain any chance of qualifying for the knockout stages of the competition.
