Blake played for the likes of Bolton Wanderers, Burnley and Bradford City, writes Tom Feaheny.
He has since been a coach at League One side Portsmouth.
Blake replaces Darin Killpartrick in the role.
"We look forward to working alongside Robbie, who has gained valuable knowledge in a very respectable playing career and, of course, at Pompey as a coach," Manager, Jack Pearce told the club's website.
"It's always exciting to bring on board people who we believe can bring fresh ideas and new energy.
"Robbie certainly fits the bill. Robbie joins us after coming to the end of his contract at Pompey working under Kenny Jacket.”