Try using
Steel-Belted Radius from Juniper (formerly Funk Software). It's a commercial product but they have a free 30-day trial download, and it runs on Windows or Linux. It's easy to get running so you can see how it operates and I have found it works brilliantly with Mikrotik after a little experimenting.
I'm still trying to get my head around FreeRADIUS as I'm still a newbie to Linux.