Sometime in November 2018, RoS released an update and that's when numerous end users had started to encounter the " Can't find fmodex.dll " bug after they avail the update. In fact, you can find a thread here about this bug.
As well, you may notice that this bug is also related to can't find fmod_event.dd and fmod_event.dll and which is quite common on Windows 7 PCs.
Driver Auto-Detect Tool for Radeon
Intel Driver Update Utility for Intel Graphics
If you have not tried, reinstall ROS to another directory in your local drive and see if it works after update.
Without uninstalling the existing ROS, try copying a running ROS installer from another PC. Put the copied the ROS files into another path and test when an update is finished.
If step 1 to 4 not working for you, then your last option is to install ROS to Windows 10 and this method worked for me. I found out that ROS works without any issue on my Windows 10 laptop so, I ended up reformating my client's pisonet machines and put back all the software overnight.