The body of Miss Roberts was discovered in the ditch next to a canal near her home in Porthmadog, Gwynedd, on April 10.
She had spent the previous evening celebrating a friend’s birthday at the nearby Union Pub.
An inquest heard that she died from both drowning and “ligature strangulation”, but they also found head and facial injuries.
Factory worker Iestyn Davies, 53, of no fixed address, appeared via video link from Manchester at Cardiff Crown Court.
Wearing a white T-shirt, Davies spoke only to confirm his name and to enter a not guilty plea.
His trial will begin on March 1, 2011, at a North Wales venue yet to be decided. Davies was remanded in custody.