I am a bit hesitant when it comes to declaring that anything has a particular sound because so much depends on system interaction. So, this is a very general statement of what I have heard. To me, Rowlands are smooth, pleasant sounding amps that don't quite deliver enough toe-tapping excitement, i.e., they are slightly lifeless sounding. I've heard them in several systems, most recently, driving Sonus Faber Anniversarios.
But, they are not offensive, and I bet they would work well with speakers that are a bit edgy and forward sounding.