If your devices are not on the supported list or if you want more advanced monitoring than what SCOM provides out of the box, you will need an additionnal Management Pack dedicated to the type of device you want to monitor.
Device vendors sometime provide one, but you will have to author it otherwise (or hire someone to do it for you).
The System Center Operations Manager - Extensible Network Monitoring Management Pack Generator tool may help you developing such a Management Pack based on a mib file, but I personally don't like that tool... I find it not very straightforward to use and the code it generates is pretty poor and unoptimized.