Both moves were announced on Friday.
Barney is hitting .224 with two home runs and 16 RBIs for the Cubs this season.
Rosscup will be making his fourth stint with the Cubs. He was 2-0 with a 2.61 ERA in 20 games with Iowa, and has pitched four scoreless innings in relief with the Cubs this season.
To make room on the roster, the Cubs optioned relievers Kyle Hendricks and Blake Parker to Iowa.