I'd rather trade Parayko if I am honest (not for RoR, just in general). I am probably in the minority on that opinion though. Parayko is considered more valuable so, we'd get more return. If the return is equal, I probably keep PArayko but would think long about it. Parayko isn't as necessary because of Pietrangelo (although we do need a RH top 4 replacement if we trade him). Parayko is better defensively, but Dunn actually has more offensive potential. I think 35+ point 2nd pair D is Dunn's floor with upside of 60 pt #2D.
Dunn didn't put up a lot of points this year but made a ton of great little offensive plays that went unrewarded. He is very elusive in small spaces with his skating which can buy time and space to make plays. He can lead the rush with his speed or make great tap-to-tape breakout passes. The biggest thing is that he is a smart and decisive PP QB, and really improved our terrible PP when he moved to PPQB of PP1. Without him, we would have been the worst team in the league on the PP. Our LD side has no good offensive D, which hurts. It would take huge overpayment for me to move Dunn
I don't move Dunn or Thomas for RoR unless there are no other options at 2C. RoR is a great 2 way C, a really great player. But Blues need more offense, ES and PP. Dunn will help provide that. RoR helps but isn't a pure offensive force.