No 50Hz motion on those boxes and I doubt they'll ever will as long as Roku keep mass producing boxes with the same spec as North America for Sky's other businesses.
However I would say that despite ITV still using 25p, the actually PQ in comparison to the 544x576 picture used on ITV3 is an improvement. (ITV, +1., 2/+1 and 4 are at 720x576 576i on Freeview)
Now that the Apple TV 4 is supporting (and promoting) 60Hz output from some streaming video applications (MLB i think), and the BBC is doing 50Hz rather than 25Hz for iPlayer, I think more and more streamers will start to support 60Hz or 50Hz full motion rather than the current 24/25/30Hz only stuff.
I'd hope ITV are aiming to match the BBC for picture quality on their online streams - and introduce a 720/50p stream at the highest tier as the BBC have. Makes a huge difference for sport and entertainment - avoiding halving the temporal resolution of online services compared to broadcast outlets.
The Roku Now TV boxes also have the bizarre situation that they only support a fixed 60Hz output (even Apple TV allows you to switch to 50Hz in the output settings option). This isn't a hardware limitation (some of the Roku boxes have the same SoC as the Raspberry Pi which allows 50 and 60Hz output - heck it even allows 24p Frame Packed 3D output...) I don't know of any current ARM SoC that doesn't allow for a 50/60Hz HDMI output.
The only reason the Now TV boxes are fixed at 60Hz for output is software... A simple menu setting to change the video format manually would be close to trivial to code.
Whilst the spatial resolution and compression artefacts of ITV 3 may be better on the Roku, if it's 25p at 60p, rather than 50i at 50p, it's still pretty unwatchably mangled for native 50i content like entertainment, sport etc. surely?