Roon is a server software and can use a tremendous amount of processing power. So, if you are running other apps and you are getting those results, it is a clear sign your machine cannot handle the processing needs for everything.
Your situation would improve immensely if you moved Roon off onto a different and dedicated machine. Getting a NUC and loading ROCK can be done pretty cheaply. Even cheaper if you don’t care about having a small box and can stick a full desktop in the corner somewhere. But, cheap is always relative. Feel free to PM for additional ideas.
It sounds like you may have some hardware issues at play if the PC is locking up with just Roon, Outlook and Excel. I would second the suggestion of getting some dedicated gear (such as Nucleus or ROCK) or troubleshooting certain aspects of the PC itself (such as checking the RAM / performing a SMART scan of the hard drive).
You can also try reinstalling Roon to see if it will help but if it is a hardware issue I don’t think it will. To reinstall Roon, you can use the following instructions:
One thing that is worth doing on Windows 10. Type background apps into the search bar. Disable all. Don’t know why Microsoft thinks that you want solitaire running in the background, but I noticed my fan noise dropping considerably one I had done this.