Initially I was thinking that this could be a big deal and my first thoughts were that this would involve creating custom profile setups for different groups with the correct language and keyboard layout defined but, as it turned out, this was not the case and this was simply a case of installing the additional keyboard layouts using good old 'Region and Language' option within control panel and then going to the 'Keyboards and Languages' tab and adding the additional layout required.
After that, in the 'Text Services and Input Languages' window, go to 'Advanced Key Settings' and verify or change the option to toggle between the two keyboard layouts. The default is to use Left Alt+Shift but this can be changed to something else if you wish.
Once set, when you launch the RemoteApp you can now toggle the keyboard layout by simply pressing the toggle command you set and away you go! Simple....as IT should be! :)