Roberts believed his neighbour was engaging in sexual acts with his friend, referred to in the judgement as "Louise".
"Auditory hallucinations convinced you to enter your neighbours' property and attack the young couple occupants of a bed with a knife. You swung a knife at the two victims, causing significant lacerations to their hands and fingers."
Following a hearing in May this year, Roberts was found not guilty by way of insanity - though the court also found he had committed the offences.
He was remanded to a secure facility until Judge Johnston could determine what should be done with him.
The court received two reports from forensic psychiatrists, as well as a letter from Roberts' current psychiatrist, and a hearing was held in early September for the court to gather more information.
According to the Criminal Procedure (Mentally Impaired Persons) Act 2003, a judge must only make an order to detain someone as a special patient if they are satisfied it is necessary in the interest of the public.
One psychiatrist described Roberts as suffering from "serious, complex, and interrelated mental health issues, with psychosexual issues a significant feature" and believed he required further treatment in a secure hospital setting.
She noted he had a history of non-compliance with medication, problems with substance abuse, and a limited insight into his own delusions.
Another psychiatrist said Roberts had "persecutory delusional beliefs and derogatory auditory hallucination", but said he had not shown an enduring propensity for violence when he was more stable.
However he required "close supervision given his propensity for violence when acutely psychotic".
Roberts' current psychiatrist noted Roberts repeatedly expressed disappointment in his actions and had stated he intended to continue treatment and avoid drug use.
"By mid-June his delusions, hallucinations and quasi-religious ideas had all stopped completely," the psychiatrist said in a letter to the court.
Judge Johnston came to the view Roberts did not need to be detained as a special patient.
His reasoning included that Roberts' history of non compliance with medication was recent and short-lived and could be mitigated by long-lasting injections. He had shown marked improvement since receiving inpatient treatment.
Roberts has also not displayed any violent tendencies while receiving treatment, and had self-reported his auditory hallucinations to his GP in the months before his offending.
"Despite possessing psychosexual fantasies, you have not acted on those fantasies since your 2010 convictions for indecent assault ... you also did not offend in a sexual manner when your mental state began to deteriorate in August 2019."
Judge Johnston felt the first psychiatrist focused too heavily on Roberts' history and assessed the current risks in a limited way.
The second psychiatrist believed special patient status might be optimal, but similar outcomes could be achieved through a compulsory treatment order instead.
"The test for special patient status requires an order to be necessary, not optimal or desirable," the judge said.
He instead ordered that Roberts be treated as a patient under the Mental Health (Compulsory Assessment and Treatment) Act 1992.
