A 34-year-old Roseburg man was in custody today accused of having sex with a 15-year-old girl at a party he threw at his home last year. Roseburg police suspect Matthew Evan Johnson furnished alcohol to her and three other minors at the March 2012 party. Sgt. Jeff Eichenbusch said the investigation was delayed because the original officer looking into the case left the police department for other employment. This year, Officer Doug Walton picked up the case and gathered enough evidence to arrest Johnson, Eichenbusch said. Johnson was booked into the Douglas County Jail on Wednesday on suspicion of third-degree …