Robson, 34 and Forte, 26 could make there debuts tonight at home to Coventry City after completing there signings during yesterday's closer of the January transfer window which ended at 11pm last night.
The pair are both contracted until the end of the season and hope to fill the void created by the departure of Nick Blackam to Reading two days ago.
Blades boss Danny Wilson told tsufc.co.uk: "When someone of his experience (Robson) and quality comes along you have to sit up and take notice. I'm delighted a deal can be completed, especially given the fact that he's been back in the country less than a week. He gives us options in offensive positions, he will score goals and be a supply line for others."
Blades-Mad are also understand that United saw a £400,000 bid turned down for Dundee United striker Johnny Russell.