The father of two was shot at the Coin Castle amusement complex at the Roxboro shopping centre on April 9th, 2009.
These new charges come nearly 3 years after gunman James Dillon pleaded guilty to murdering Roy Collins.
It's believed the motive for the shooting could be traced back to 2004 when a member of the businessman's family reported a crime to Gardai, implicating a member of the Dundon-McCarthy gang who was subsequently jailed.
After years of threats Roy Collins's family moved abroad last year believing they had no other choice.
The two men due up in court today are currently serving sentences for other matters – one of the men is aged in his 30s. He is suspected of ordering the killing.