Sport says United are interested in Roberto leading up to the January market and believe he is unsettled at Barca.
The 21 year-old has been likened to Xavi and was expecting to see more first team action this season following the departure of Thiago Alcantara to Bayern Munich.
But Roberto has remained on the outer and is now weighing up his options.
United are preparing a €6 million offer for the midfield schemer ahead of the winter transfer window.
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball