Download the latest desktop app to a shared with everyone folder on your windows server, Create a script folder share it with everyone and write a script that will run each time a user logs in, ie.: rocketchatdeploy.bat:
if not exist %LOCALAPPDATA%\Programs\rocketchat\ (goto GO) else (goto STOP):GO
if not exist %APPDATA%\Rocket.Chat\ md %APPDATA%\Rocket.Chat\
copy /y \\ad01\Softwares\config.json %APPDATA%\Rocket.Chat\
msiexec /i \\ad01\Softwares\rocketchat-setup-3.4.0.msi /quiet
config.json = you can customize the server URL on this file, so when you deploy to all machines, they will be pointing to the same and correct rocket.chat server.ad01 = your server name, remember to share the folder with everyone.
Attach it to a GPO:
That's it, the summary would be:
if the folder %APPDATA%\Rocket.Chat\ doesn't exist, it will be created then the config.json file will be copied to the folder, and after that, Rocket.Chat app will be silently installed.