Not seen Matty Russell play recently but I always thought he was a strong ball carrier and a solid if not spectacular player. His strong ball carrying will likely suit the way Rohan likes to play.
I would much rather him on the wing than Roberts, given Fusitua and Lumb's injuries.
Whilst I don't think Roberts is a good winger, he is a solid centre and has been fairly safe under the high balls and in defence. I would not criticise him as he has always given his best, even if sometimes his best is not good enough.