I went the other way - from Roomster(s) to Yeti.
I love my Yeti and there is no other car currently available (from any manufacturer) that I like more. But I consider my Roomster Scout 1.9tdi the best car I have owned in fifty years of motoring. It was comfortable and flexible, and it would take all my camping gear. It also moved a split base double bed, mattress and two bedside cabinets in one trip. It also had the fixed pano roof, which I miss dreadfully. Sadly, the return of an old knee injury forced me to part-exchange my Scout for another Roomster with DSG.
My Roomster SE 1.2 DSG was a nice enough car but I found the (softer) driver's seat far less comfortable than the Scout and I was unable to drive it for more than half-an-hour before the discomfort became unbearable.
One of my biggest criticisms of the Yeti is that the spare wheel lies on top of the floor and takes up an enormous amount of boot space. The spare wheel on the Roomster is let into the floor and takes up no boot space.
If Yeti and Roomster Scout were still available new, I would choose the Roomster in a heartbeat.