My footswitch for my Rockerverb has died and I was wondering if a Hiwatt Fs200 footswitch would work for switching both the channel and inbuilt reverb on the amp?

Gibson Les Paul Traditional Satin
Fender 72' Thinline Telecaster
Fender Am Telecaster
Bad Cat HotCat 30R

Korg Pitchblack
Xotic BB Preamp
TC Flashback X4
Strymon Timeline
JHS Double Barrel
Most dual button footswitches have a stereo plug on them, which won't work on the Rockerverb without modification. Looks like you already know this because it looks like the Hiwatt one is perfect for the job as it splits into two mono plugs.

I'd say yes, go for it. Only negative is it doesn't have LED indicators.
These go to eleven...