Arca was instrumental in The Black Cats 1-1 draw with their North East rivals on Saturday and Robson admitted The Magpies did try and sign him before he moved to Sunderland.
"I was interested in him but Sunderland had more money than we did so they went ahead and did the deal," Robson said.
"He is a clever player, he is young and he can only get better. I like him."
Black Cats boss Peter Reid was full of praise for the 19-year-old international and identified him as the best player on the pitch in the Tyne-Wear derby.
"He was absolutely outstanding," Reid drooled. "Every time he got the ball even I enjoyed watching! He has got a tremendous brain, he is getting stronger and he is still only 19. Wait until he grows up.
"I don't like to put any pressure on players but certainly he is an exciting talent."
His sentiments were backed up by Arca's team-mate Don Hutchison who believes the Argentinian had 'his best game in the Premiership so far.'
"He is certainly a player that will be really crucial to us in taking Sunderland to the next level," Hutchison said.
Arca has already started 25 games for Sunderland despite being brought as 'one for the future.'
