Just to let everyone know incase anyone was interested, that possible Roberts badged as a Rossin on ebay is approx 52/53cm c-c seat tube, and what looks be 52cm c-c top tube. I asked the seller-also asked for the frame number but sadly he hasn't given me that.
https://www.ebay.co.uk/itm/Bike-Frame-Rossin/124258765563?pageci=2c8d1f66-7904-41ed-9f30-68bdf95ab07f Bargain Roberts badged as a Rossin on eBay