Sussex Police said between 4.49pm and 6.15pm on Thursday, October 15, the 16-year-old victim was with a group of friends when he was approached by two unknown men.
A spokesman for the force said: “One of them assaulted him and stole his gold ring, while the other stole his trainers before returning them a short while later.
“Following this, the suspects ordered one of the other youths to hit the victim in the face several times, threatening violence if they failed to do so.”
Police said one suspect was white with dark blonde hair, wearing grey tracksuit bottoms, a grey jumper and black trainers.
The other was white, with a small ponytail, wearing a black puffer jacket with a fur lined hood, a grey tracksuit top and grey tracksuit bottoms.
They are believed to have made off in the direction of Haywards Heath railway station, said police.
A spokesman added: “A 21-year-old man from Chichester, arrested on suspicion of robbery, has been released on conditional bail until November 15, pending further investigation.
“A 24-year-old man from Haywards Heath, arrested on suspicion of robbery, has been released on conditional bail until November 13, pending further investigation.”
Police are appealing for witnesses to the robbery. Anyone with any information about the incident is urged to report it online or call 101, quoting serial 1141 of 15/11.
They can also contact the independent charity Crimestoppers anonymously on 0800 555 111 or report it online.