The victim, who police say was known to them, was estranged from his family.

"He hadn't had any contact with his family for a long time," the police officer said.

No missing persons' report was filed.

On Friday, Chatswood acting Superintendant Simon Jones told reporters that it was clear, despite its decomposition, that the body had sustained "a number of injuries".

"We must treat the death as suspicious. It is believed the body has been in the home for a considerable time. The body was covered in an amount of material," he said.

Acting Superintendant Jones said the man's death was both "unnatural" and "very suspicious".

He said that Mr Roberts' hoarding made investigating the home challenging and "not very pleasant for investigators".

Dog squad officers and detectives remained at the house on Friday and numerous items have been seized, including clothing from the body.

The ramshackle property was being cleaned to deal with Mr Roberts' will.

Mr Roberts' body was found in the house after a worker from the local IGA became concerned when he did not come into the shop daily, as was his custom, and went to check on him.

Upon realising the bins at the property hadn't been taken out, the supermarket employee called the police who entered the house and found Mr Roberts' body.

Almost a year later, police are asking what role, if any, Mr Roberts had in the death of the man whose body was found last week.

Neighbours characterised Mr Roberts as a "recluse" and a strange man.

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“He was [in his] late 50s or 60s, had the same brown jacket on. He was childlike in a way. He just had no expressions, nothing,” a neighbor told the ABC.

“You’d say 'hello' and he’d just mutter 'hello' or just not notice. He lived in this tiny little house on the corner. It’s completely overgrown, and you can see rubbish in the garden.”

Gayle Meagher, a long-time neighbour, recalled exchanging pleasantries with Mr Roberts.

“He was a bit of a recluse,” she told the ABC on Thursday.

"It's creepy and sad, it's just awful that it's next door, very unpleasant," Mrs Meagher said.

Police are urging anyone with information to come forward.