The OpenStudio installer and uninstaller both use the Qt Installer Framework (https://doc.qt.io/qtinstallerframework/). I believe the current version of OpenStudio, 2.7.0, still uses Qt Installer v2.0.3, but in any case, you can write a short script to automate this. I was able to uninstall OpenStudio with the following script, by calling

C:\openstudio-2.7.0\maintenancetool.exe --script=uninstall.qs

Then, my uninstall.qs looks like this:

function Controller() {
    }
Controller.prototype.IntroductionPageCallback = function () {
    gui.clickButton(buttons.NextButton);
}
Controller.prototype.ReadyForInstallationPageCallback = function () {
    gui.clickButton(buttons.NextButton);
}
Controller.prototype.FinishedPageCallback = function () {
  gui.clickButton(buttons.NextButton);
  gui.clickButton(buttons.FinishButton);
}