Omar "OJ" Koroma joined Norwich City on 4th August 2008 on a season long loan from Portsmouth who had just signed him from Banjul Hawks on a two year deal.

The Gambian striker had previously trained with both Watford (October 2007) and Southampton before emarking on a two week trial in July 2008 with Portsmouth, featuring in some of their pre-season friendlies and impressing enough to be offered a contract. He was elligable for a work permit after recently marrying a British partner.

Norwich boss Glenn Roeder told BBC Radio Norfolk: "Koroma looks exciting and full of enthusiasm, but I don't want to put too much pressure on him."

Portsmouth manager Harry Redknapp believes that Koroma has a big future at Fratton Park."I've been very impressed with him and I'm pleased that we've got him here. I like him very much. He's a good kid and he's got the potential to become a very good player.

In late December 2008, Koroma suffered a serious ankle injury, which necessitated surgery. This took place in January 2009, leaving him a likely recovery period of 10 to 12 weeks abd so the loan was cancelled and he returned to Portsmouth at the end of January 2009.

Koroma's opportunity to prove himself in the Pompey first team may be enhanced following their relegation to the Championship at the end of 2009/10 but instead he was released from the club in May 2010

After trialing in Denmark with Brondby, he joined Conference National side Forest Green Rovers on trial and scored a brace in a 2-1 reserve team victory over Crawley Town on 23rd April 2012. He signed a three year contract with them on 21st May 2012. Koroma is the fourth new forward to join Rovers following the arrival of Magno Vieira, Ben Wright and Phil Marsh.

Rovers manager Adrian Pennock released Koroma on 23rd January 2014.

Following a brief trial, he joined Dulwich Hamlet  in November 2014, making his debut against Maidstone United on 12 November 2014, before going on to score his first goal for the club in a 3-1 away win at Harrow Borough on 22nd November 2014.

After leaving Dulwich, he moved to Iceland to sign for Thróttur Reykjavík on a one-year contract. On 1st March 2016, he signed a one-year contract with Kazakh side FC Kyzyl-Zhar SK.

He returned to England in the summer of 2016, signing for Wealdstone having trialled with Dulwich Hamlet earlier in the summer. He then spent time at Dulwich before joining Carshalton Athletic in 2017/18 helping them win the Isthmian South Division title in 2017/18. He spent the latter part of 2020/21 at Worthing.

He moved to Merstham at the beginning of November 2022.