He kicked in the side door to the garage triggering another alarm, but killed the sound after climbing a ladder and cutting the wires.
After a thorough search, Robertson discovered a firearms safe and took a 12 gauge shotgun, a .22 rife, three bolt action rifles and an air rifle, as well as 150 rounds of ammunition and a belt with 12 rounds of shotgun ammunition.
Along with the firearms, he found a cash card with the pin number attached.
After loading them into his car, he ripped the two safes from a wardrobe using a sledge hammer and Jerry bar and wheeled them to his car using the owners' wheelbarrow.
The next day he attempted to use the stolen card at a Hastings ATM, but the first transaction was declined. The second attempt was successful and he withdrew $500 by using the card's pin number.
Robertson then travelled to Waipawa and attempted to make two more transactions at an ATM - but both were declined.
During the next few days he managed to open both safes using a splitting axe and discovered jewellery of 'significant monetary value'.
He bagged up the jewellery and took it to an associate who caused huge damage by removing some of the stones from the jewellery pieces.
Police searched a Flaxmere address on February 14, discovering all the stolen firearms, jewellery and both safes.
When spoken to by police he told them he had 'no money, no nothing and wanted to get some more drugs.'
His defence counsel Clint Rickards told Judge Butler that Robertson was 'going through a rough time' and that the burglary was 'opportunistic' rather than pre-meditated as he was staying down the road.
Rickards also told the court he didn't commit offences when he was in a 'stable environment' and was 'certainly apologetic' for his actions.
Judge Butler disagreed that the burglary was opportunistic and sentenced Robertson to two years and three months in prison.
