Andy Iro of Stevenage and George Barker of Brighton both signed on loan until January while Melvin Holwijn also joined on non-contract terms before Thursday's 5pm close.
Both loan players go straight into Saturday's squad to face Cheltenham but Holwijn still awaits international clearance.
Robson told the club's official website: "We're now delighted to have Andy in on loan to further strengthen our defensive line. He's 6ft 5in, has plenty of experience and we hope he'll be an asset for us at both ends of the pitch.
"George potentially has a lot to offer us. He's a natural goalscorer who hasn't been given an opportunity at Brighton - we hope by coming here to Barnet that he'll gets the opportunity to show his qualities."
Director of Football Paul Fairclough added: "Melvin is an exciting and very quick, rapid forward."