The 21-year-old has not played for the first team since joining last month.
But boss Gary Johnson, who only arrived at the club last week as replacement for Brian Tinnion, is hoping to have a better look at his credentials.
He said: "Rob came on board before I got here so I haven't seen too much of him.
"The extension has gone through which means we've got him until the end of October with a view to adding another month on top of that as well, so we'll see how things go."