Mr Riley died in hospital of a stab wound to the chest on June 27.
Police had been called to Darley Avenue in Athersley the previous night following reports that he was seriously injured.
A 33-year-old man from Barnsley was arrested on suspicion of assisting an offender yesterday (Wednesday September 2).
A 21-year-old man, also from Barnsley, was also arrested on suspicion of possession with intent to supply.
Both have now been released under investigation.
Martin Wilson, 37, of Monsal Crescent, Athersley, and Julie Evans, 40, also of Monsal Crescent, appeared at Sheffield Crown Court in July.
Wilson was charged with murder, and Evans charged with assisting an offender, and both remain in custody.
The pair will return to Sheffield Crown Court on December 7.
Detectives continue to appeal for information as part of their inquiry.
If you have information that may help their investigation, call 101 and quote incident number 1227 of June 26.