I recommend to all Synology NAS fellows with upgraded RAM to disable the memory compression enabled by default.
Without going into deep technical details, if you upgraded your RAM then uncheck this feature. This feature taxes the CPU because it takes care of the compression and decompression process to save RAM.
How? Control Panel / Hardware & Power / General / Memory Compression. Uncheck and restart.
You should experience a much smoother Roon interface after.
Enjoy!