The talented attacking midfielder spent last season on loan at the Tigers from Forest Green Rovers.
After a string of impressive performances - and the odd long-range rocket, Mike Cook made his stay permanent.
“I am very happy to be officially a player of Gloucester City," Robert told the club's website. "The entire club has been magnificent since I have joined them last season.
"The club wants to grow and be more ambitious in the future, which is great, with some exciting days coming with the new stadium.
"We are building something special that I want to be part of. The fans showed me so much love from day one that I feel like I am coming back home.”
Mike Cook added: "We know there was keen interest from Football League, National League and other National League North teams. To get Fabs signature is a credit to the club"
Gloucester City open their National League North season on August 3 with a trip to Blyth Spartans.
You can access a full list of the Tigers' fixtures by clicking here.